Very lean at idle RPM/MAP problem

[jnorris]

This problem is on a 1998 Z28 A4 with a 230/230 cam, ported heads, and LT headers.


The lean condition only exists when on the SD tune. With the MAF I do not have this problem.

On cold starts my AFR will be in the 16 – 18:1 range for 5 to 10 min even though the OLAF table has an AFR of 13.3:1 at the idle RPM/MAP. With the scan tool I have confirmed a commanded AFR of 13.3 but my WB shows very lean and the car idles like it is very lean.

As an experiment I richened up the AFR in the OLAF table to 11.0x at 20c and tapering it up to 14.63 at 70c. This corrected the cold start lean problem. Commanding an AFR of 11.2:1 netted a real AFR of 13.2:1. As the car warmed up the difference between the commanded and actual AFR lessened. However as soon as the ECT hit 70c the AFR went lean at 16.x:1 at idle MAP. At driving RPM/MAP the AFR was 14.7:1. After about 5 min of driving the AFR at idle went back to the commanded 14.63:1

There seems to be evidence that there is another table or parameter that is affecting the AFR at idle (on the 98s) for a period of time just after startup. Every restart is going lean if the car has been sitting for 30min or more. If I just turn the car off and restart it within a few min the lean condition is not there.

Other possibilities:
I thought about how I had lowered the IAC effective area table (drilled TB) and thought that maybe there was additional air coming in the IAC/TB hole that the PCM was not aware of and therefore not compensating for. As an experiment I changed the table from 4 positions down from stock to 3 positions down from stock and flashed the PCM. On the startup the AFR went lean at 16 – 17:1. My IAC correction is only off by -.71.

Maybe an idle airflow table being off might cause my lean problem and the lean time on restarts is the time it takes the PCM to learn out the bad values. I might need to put the IAC effective area table back to stock or lower it 6 positions from stock and see what happens.

As I thought more about it I remembered that I had cut my VE while cranking table by 40%. I loaded the stock table back in and flashed the PCM. When I started the car the idle AFR went lean to 17-18:1 so this did not solve the problem

Any thoughts or suggestions?


Thanks

John

[WicketMike]

i was having the same exact problem last week on my 98'.

I posted some threads about it. i didnt get any help.

Once the car reaches 170 or so. it goes back down to 14.63 but at the lower temps its really lean 18-19.1 afr.
I tried driving it before it reached the correct temp and it stays lean even while driving, so i had to stop and let it idle some more to reach the higher temp.

[ringram]

I think you dudes will have to pump up your ve tables.
While in open loop (cold ect) fueling will be mainly determined by a correct ve. If you are running lean you need to bump up the ve in the area of rpm vs map. With the maf plugged in its correcting the bad ve for you.

Have you dialed in your VE tables using a wideband or ltft's? if not try 10% in the idle area and see what happens.

If it works post off your order for an LC-1 or equivalent wideband, it will dial in your ve fast and easy. ltft tuning is tricky as it averages the whole ve table adjustments over a limited number of cells. 9 or so from memory..?

[WicketMike]

if we bump up the idle area it will be 10% to rich after the car warms up.
its only during the warm up period. Once it hits the desired temp. 170-178?? then its fine. This is with the maf unplugged

[ringram]

Ok, but dont forget once its warm you go into closed loop and the o2 sensors will make it run at 14.63:1 whatever happens anyway, whether its lean or rich they will compensate.

Can you paste your ltft tables here?

[jnorris]

Ok, but dont forget once its warm you go into closed loop and the o2 sensors will make it run at 14.63:1 whatever happens anyway, whether its lean or rich they will compensate.

Can you paste your ltft tables here?


We are running in open loop speed density mode and once the car has been running for 5 -10 min the commanded AFR matches the WB AFR.

John

[ringram]

Oh ok, sorry I thought you were in closed loop. Should have checked first.

[jnorris]

Oh ok, sorry I thought you were in closed loop. Should have checked first.


No problem. I appreciate the feedback.

John

[jfpilla]

Let my try this. I see the same thing when in SD. It looks as if Charge temp. blending{B4901} and PE mod. based on coolant temp.{B3617} are the cause. Unless it's coincidence. When I apply the factors from both tables, to Commanded, the value I get is pretty close to actual logged. I also noticed that as MAFg/s go up the actual AFR richens. Since MAFg/s affects the blending factor that also makes sense. I'm curious too. :???:

[Black02SS]

How can B3617 be the cause? If the car is at idle I don't see how a PE table can effect it. I too have the same problem and I notice a trend here... All three of us have 30# SVO's... Coincidence..

[WicketMike]

How can B3617 be the cause? If the car is at idle I don't see how a PE table can effect it. I too have the same problem and I notice a trend here... All three of us have 30# SVO's... Coincidence..

i have stock injectors

[bink]

Injector offset table????

[jfpilla]

How can B3617 be the cause? If the car is at idle I don't see how a PE table can effect it. I too have the same problem and I notice a trend here... All three of us have 30# SVO's... Coincidence..

I don't know what the cause is but I'm curious. Not concerned, just curious.
Doesn't the car use PE for some time after startup? If it doesn't then B4901 gets the change to within 1 point or so short or another table could be involved or my extrapolation could be bad. B4901 seems to be involved since the AFR does richen as g/s increases.

I don't think the injectors are the issue in SD at startup.
However, if they don't flow as advertised, it may be one reason for commanded and actual AFR not matching up in WOT PE.

[Blacky]

Try changing your injector timing at cold start temperatures to the same timing value at normal operating temperature.

I have no reason to believe that will solve anything, other than it causes a difference at different operating temperatures, which is the only clue that is available.

Just thowing ideas into the ring.

[jfpilla]

Injector offset table????

Hey Joel,
The offset table does not reference temperature in HPT or EFI but I think it does in Edit. The injector timing tables do reference temperature, so they could be involved.

Someone let me know if B3617 is or isn't involved in open loop when not
WOT.

[WicketMike]

Try changing your injector timing at cold start temperatures to the same timing value at normal operating temperature.

I have no reason to believe that will solve anything, other than it causes a difference at different operating temperatures, which is the only clue that is available.

Just thowing ideas into the ring.

that could be it B3702, because at 176f (80c) is when that table reaches its highest setting. which is the tempature i am seeing where it richens back up to where its suppose to be.

[Black02SS]

that could be it B3702, because at 176f (80c) is when that table reaches its highest setting. which is the tempature i am seeing where it richens back up to where its suppose to be.
jnorris point this out to me as we were discussing this the past few days and I agree that I "think" it may help the issue. I won't be able to test my theory until Monday.

Hey Paul/Ross - Is the car in PE at all upon startup?

[jnorris]

Here is what I have tried last night and today and the results.


Changed the OLAF table idle AFR at low ECT temps. back to the 13.3 values which were 11.2 to offset the lean condition.
Put the stock IAC Effective area table.
Used the 2002 B3702 and B3703 tablesAlthough the commanded AFR at low ECT did not match my WB the AFR was not 17 – 18:1 lean but was in the 15.8:1 range. As the ECT increases the gap between the command AFR and WB AFR narrowed. This was a cold start.

Today I saw jfpilla’s post about B4901 and B3617. I zeroed out the B3617 table and flashed the PCM. When I started (ETC =21c cool start) the car the AFR was still a little leaner than the commanded AFR. In the 1st min the commanded AFR avg was 12.49 and the WB average was 14.3. Within 2 min of the startup (ECT = 50c) the commanded AFR and the WB AFR were within .3 points of each other.

I think that with some tuning of the OLAF table in the cool ECT at idle MAP this lean startup problem can be solved.

So overall I had good success with resolving my lean start problems. Tomorrow morning will be the real test.

John

[jnorris]

My take on B3702 Injection Timing and B3703 Injection Timing Trim tables.

By the description of these tables it seems that they are values that the PCM uses to open the injectors earlier in the piston cycle based on ECT. The IPW stays the same.
At 6000 RPM 2.5 – 5.5ms is not significant. These tables will have the most affect on fueling at low RPMs.
In looking over stock flash files the 99-02 F-body (A4 and M6) cars are the same, only the 98s are different. The few Corvette files I looked are different than the F-body cars.

On the 98 A4 Vette the Injection Timing Trim table is the same and the Injection Timing table is about .2 higher.

Are the difference in these values from 98 and 99-02 PCM driven?

John

[Black02SS]

I have already zero'd out B3617 on my tune but still see it. I need to check to see if I can't find the post you are refering to.



Here is what I have tried last night and today and the results.

Changed the OLAF table idle AFR at low ECT temps. back to the 13.3 values which were 11.2 to offset the lean condition.
Put the stock IAC Effective area table.
Used the 2002 B3702 and B3703 tablesAlthough the commanded AFR at low ECT did not match my WB the AFR was not 17 – 18:1 lean but was in the 15.8:1 range. As the ECT increases the gap between the command AFR and WB AFR narrowed. This was a cold start.

Today I saw jfpilla’s post about B4901 and B3617. I zeroed out the B3617 table and flashed the PCM. When I started (ETC =21c cool start) the car the AFR was still a little leaner than the commanded AFR. In the 1st min the commanded AFR avg was 12.49 and the WB average was 14.3. Within 2 min of the startup (ECT = 50c) the commanded AFR and the WB AFR were within .3 points of each other.

I think that with some tuning of the OLAF table in the cool ECT at idle MAP this lean startup problem can be solved.

So overall I had good success with resolving my lean start problems. Tomorrow morning will be the real test.

John

[jnorris]

To confirm that the B3617 table truly had an affect on the cold ECT AFR I loaded PCM files with and without this table being zeroed out. With the table at stock values and zeroed out the AFR on the WB was the same. I have put this table back to stock.

I have for the most part corrected my cold ECT lean problem by putting in richer than desired values at low ECT idle MAP positions in the OLAF (B3605) table and using modified 1998 B3702 and B3703 tables. See below:

B3605 at MAP 50-55/-10c-70c
12.070636
12.070636
12.070636
12.070636
12.070636
12.524798
13.094107
13.895787
14.628573

B3702 and B3703
2.550781
2.550781
2.550781
2.550781
2.550781
2.550781
3.550781
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688

[WicketMike]

thanks for the info, so it looks like you fixed it.

did you try leaving b3605 alone and only raising the b3702 and b3703 to 4.55 across the board?

[Black02SS]

Thanks for the info John. I have cleared out my PM's now so they should work.

[jfpilla]

Thanks for the info, John and clearing up the question about 3617. I'll try it next week.

Back to your original question. Why is A/F different on cold start with, versus without, the MAF? On cold start, with either, they are in open loop. Or has your solution fixed both states?

[WicketMike]

editdddddddddddddddddddddddddd

[bink]

Thanks for the info, John and clearing up the question about 3617. I'll try it next week.

Back to your original question. Why is A/F different on cold start with, versus without, the MAF? On cold start, with either, they are in open loop. Or has your solution fixed both states?

Joe - my bad on the offset table suggestion- I dont know what I was thinking!!:nixweiss: :D


Through the MAF the PCM goes through the airmass calculations and crutches the predicted airflow- crutched injector pulsewidth determination.
Without the MAF (SD) it's more straight forward using the VE table, IAT, MAP, RPM etc.
Open Loop - no O2 sensor input.

gameover posted this AIRMASS Calculation info on LS1Tech ... it really helped me get a little better understanding of fueling via the MAF versus SD. At one point in time I had three copies of this Airmass post conviently scattered around the house so I could review it as the need arose. True - hardheaded analog man :Eyecrazy: . AIRMASS Post -->http://www.ls1tech.com/forums/showthread.php?t=147645
I realize you know ALL of this......... God knows the number of times I've not had them straight in my head - I'm embarrassed to think about the hours I've wasted !!.

Cheers,
joel

[jnorris]

Well I really did not fix the problem; I just covered up the symptom.
Actual AFR verses commanded AFR differed by an average of 2 points during the 1st min of the cold start.
The next min the AFR was off by 1.2 points, the next by .8 points, and the next min by .5 points.
See attached picture. The bottom graph is the WB AFR (yellow), commanded AFR (blue), and ECT (green)
http://img.photobucket.com/albums/v623/jnorris404/th_SD_ColdStart.jpg (http://img.photobucket.com/albums/v623/jnorris404/SD_ColdStart.jpg)



Why is this happening? Well I had the idea that maybe the purge solenoid was being commanded on up to a certain temp by default if there was MAF failure. I logged GM.EAVPDC but it was never commanded on. I knew it was a stretch but I did not know of any other way air could get into the engine.

With a MAF tune there is not a cold start lean condition. But on the next cold start I will check.


John

[jfpilla]

Joel, John,
I'm only referring to the short time after startup, in open loop, with the MAF. In this state it's lean but not as lean Mafless startup. It appears that Joel is making me read and learn about this.
Joel,
I have not spent any time at all on this part of tuning. I run the MAF and only use SD to tune the VE's and really have not paid attention. My goal has been to get idle and cruising tuned using as few tables as possible.
It will be interesting to work on something new.
Thanks for the help.
Joe

[Black02SS]

Joel, John,
I'm only referring to the short time after startup, in open loop, with the MAF. In this state it's lean but not as lean Mafless startup. It appears that Joel is making me read and learn about this.
Joel,
I have not spent any time at all on this part of tuning. I run the MAF and only use SD to tune the VE's and really have not paid attention. My goal has been to get idle and cruising tuned using as few tables as possible.
It will be interesting to work on something new.
Thanks for the help.
Joe I believe jnorris stated to me before that he didn't notice the car runing lean with his MAF plugged in. I am going to re-install my wideband tonight and will be able to help you guys out as it is colder then snot here.

[bink]

Joel, John,
It appears that Joel is making me read and learn about this.
Joel,
I have not spent any time at all on this part of tuning. I run the MAF and only use SD to tune the VE's and really have not paid attention. My goal has been to get idle and cruising tuned using as few tables as possible.
It will be interesting to work on something new.
Thanks for the help.
Joe

Joe ...HeHehe...... I know you know this!

I often get it confused...that's why I elaborated a bit.

The AIRMASS reference is for any and all lurkers/newbies. I always try to think of the newbies. You guys helped me out (as a newbie) immensely - I try not to forget that.

Cheers,
joel

[jfpilla]

Joel,
I wasn't being sarcastic. The link didn't work when I answered you. Link:http://www.ls1tech.com/forums/showthread.php?t=147645

I misread jnorris' post and thought he had the same question as I have. I've been thinking about why at cold startup, when still in open loop, the AFR is lean with the MAF and at the same conditions, 2 points leaner with the MAF disconnected? With the MAF it goes right to commanded as soon as the STFTs come on.
In both cases as soon as I start driving commanded is matched. Driving in cold state will cause it to match also. I'm wondering if my WB is getting lazy but that doesn't explain the difference with and without the MAF. Unless, with the MAF in open loop other tables have an affect. But the tables I know of would richen A/F. So, back to injector timing. Might the bigger injectors need to have their timing increased. Fueling does get reduced in the course of tuning for our types of mods. That's next.
Cheers:notacrook: Go Panthers, Go Steelers :notacrook:
Joe

[jnorris]

Joe - my bad on the offset table suggestion- I dont know what I was thinking!!:nixweiss: :D


Through the MAF the PCM goes through the airmass calculations and crutches the predicted airflow- crutched injector pulsewidth determination.
Without the MAF (SD) it's more straight forward using the VE table, IAT, MAP, RPM etc.
Open Loop - no O2 sensor input.

gameover posted this AIRMASS Calculation info on LS1Tech ... it really helped me get a little better understanding of fueling via the MAF versus SD. At one point in time I had three copies of this Airmass post conviently scattered around the house so I could review it as the need arose. True - hardheaded analog man :Eyecrazy: . AIRMASS Post --> http://http://www.ls1tech.com/forums/showthread.php?t=147645


I realize you know ALL of this......... God knows the number of times I've not had them straight in my head - I'm embarrassed to think about the hours I've wasted !!.

Cheers,
joel


Good info...Thanks

Below is the part that caught my eye. Was there ever any “more” posted about this?


There is another way to disable the MAF system completely (ie. without setting the DTC's) and by tuning of the thresholds and other flags you can get a fully functional SD tune happening, the so called "True Speed Density Mode"... maybe more on that later...

[jfpilla]

I installed a SD tune. Tried B3702(inj. timing) and nothing changed. Tried B4901(Charge temp.blending) and WB still read 18:1 but the car idled like hell. I rechecked the VE's and they are fine.

I give up and will chalk up this issue, in my car, to a weak WB sensor and Long Tubes causing the sensor to take a while to warm up.:nixweiss:

[jnorris]

I believe jnorris stated to me before that he didn't notice the car runing lean with his MAF plugged in. I am going to re-install my wideband tonight and will be able to help you guys out as it is colder then snot here.

Today I put my MAF tune back into the car and did a cold start. It took my WB 30 seconds to warm up but after it did the WB AFR was tracking with the commanded AFR from the start up temp to 77C.
Overall the MAF tune runs much better than my SD tune and I did not have to do anything to trick the PCM in order to get the correct AFR. I will keep the MAF tune in the car for a while.

John

[Black02SS]

Guys, if it takes less time for the car to start tracking with the wideband, couldn't we assume that maybe there is another table that needs adjustment on cold starts (maybe one we don't have)? If you think it is the sensor, would it make a difference if you let the sensor warm up for longer then the 30sec inital period before you start the car?

[jfpilla]

John,
My car runs great with the MAF and I like the fact that the trims adjust for changes in weather. My car stayed in Open Loop for just under 2 minutes(from 17C to 33C)with the MAF and also went right to tracking Commanded. That's why I quit on the exercise of why lean in SD.
Chad,
I don't know if we can assume another table but I sure wish there was a fueling table based on IAT.
I don't think it's a good idea to heat up the sensor without the engine running. I believe that moisture in the pipe can hurt it. At least that's what I've read and it makes sense.
Good thread, it's been fun.http://efiforum.iqd.co.nz/images/icons/icon10.gif
Joe

[WicketMike]

Just to let you guys know, incase you havent tried it.

the lean condition isnt just at idle. if you drive the car while it is in the lean condition before it warms up, its still a good 2 full points lean

I dont get the lean condition at startup all the time.
This morning i started the car and the AFR was fine and i started to back out of the garage and by the time i got to the street to take off, it was super lean. So for some reason it didnt get really lean until i put it in gear. i dont know if that helps or not

[jnorris]

My car is the same way. The fueling is very inconsistent until the car is fully warmed. This is why I went back to the MAF.

John

[ringram]

I use the Custom OS A0014 table and dial in 1% ve change every 10deg C.
Works well. I had noticable difference until I did this, now afr tracks commanded pretty much all the time bang on.

[WicketMike]

today, instead of letting it warm up while being lean, i went into the scanner and took over the auxillary systems (F5) and made it rich manually. I set it to 12.5 which made the actual around 14.5-14.7

When you take it over, what table are you taking over? would that help?

[Blacky]

today, instead of letting it warm up while being lean, i went into the scanner and took over the auxillary systems (F5) and made it rich manually. I set it to 12.5 which made the actual around 14.5-14.7

When you take it over, what table are you taking over? would that help?

It doesn't "take over" any particular table. The normal PCM fuel ratio is always computed. If the AFR is being overridden by the Scan Tool, that computed AFR figure is replaced by the value sent from the Scan Tool.
(I don't know why the commanded is different form the override.)

Paul

[deezel]

Do you guys have B3642 table? (Initial coolant temp enrichment)
I think that adjusting this table could provide a solution to your cold start issues without VE or injector adjustments.

[Black02SS]

Do you guys have B3642 table? (Initial coolant temp enrichment)
I think that adjusting this table could provide a solution to your cold start issues without VE or injector adjustments.
In my OS the number is B3632. This table is a EQ Adder table to the OLFA Table B3605. If you adjust this table it will also adjust your Commanded AFR. The problem isn't what we command, it what we see on actual upon start. We can "make" the actual show 14.63, but that means like menitoned above, the commanded afr has to be really rich (12.5).

[deezel]

I realize that using the "Initial coolant temp enrichment" table does not identify the root cause of your cold start mixture issues. However, if it solves the lean cold start problem, how much does it really matter what the root cause is? The problem you describe (AFR does not match commanded after cold starts, then gradually approaches commanded at normal operating temps) seems to match that table (AFR adder vs coolant temp after startup). Why not use it to fix the problem?

I suspect some of the other suggestions in this thread might be contributors to the problem (injector tables for example). But those seem to be trickier to tune properly. Good luck with your tuning.
:cheers:

[Black02SS]

I realize that using the "Initial coolant temp enrichment" table does not identify the root cause of your cold start mixture issues. However, if it solves the lean cold start problem, how much does it really matter what the root cause is? The problem you describe (AFR does not match commanded after cold starts, then gradually approaches commanded at normal operating temps) seems to match that table (AFR adder vs coolant temp after startup). Why not use it to fix the problem?

I suspect some of the other suggestions in this thread might be contributors to the problem (injector tables for example). But those seem to be trickier to tune properly. Good luck with your tuning.
:cheers:
For me the main reason is to find out why it is doing what it is. I have the problem "fixed" but would like to understand why the PCM does what it does or how it does it. :cheers:

[Blacky]

I use the Custom OS A0014 table and dial in 1% ve change every 10deg C.
Works well. I had noticable difference until I did this, now afr tracks commanded pretty much all the time bang on.

The PCM is a little "brain dead" in SD mode when dealing with different IAT temperatures. If the IAT is colder than when the VE table was tuned, then the air is denser and packs more oxygen. SD mode using the VE table* does not compensate for that. The MAF does compensate for changes in IAT.

*Strangely the Cranking VE table does compensate for IAT changes - probably because 9 times out of 10 the engine is cold when cranking.

This is the inverse of the effect tuners were seeing after getting fuel trims perfect on a cold day and then seeing fuel trims going 1 or 2 AFR richer on a warm day. That is why {A0014} was added.

I think Ringram has hit the nail on the head by using that table to solve the problem.

Regards
Paul

[WicketMike]

This is the inverse of the effect tuners were seeing after getting fuel trims perfect on a cold day and then seeing fuel trims going 1 or 2 AFR richer on a warm day. That is why {A0014} was added.

I think Ringram has hit the nail on the head by using that table to solve the problem.

Regards
Paul

but you have to have a custom O.S. and we cant upgrade because we have 98's, correct?

[marcink]

Guys, do you have this lean condition on cold SD startups only? I have the same situation but in my case it happens after any startup - also when engine is hot (but the whether was cold at that time) - for the first few minutes.
I tried to find any dependencies but they are not obvious. What I have observed though is that the alternator voltage is higher after every engine start (like >15V) and than gradualy decreases (to 13.8-14V). So I started to thing about Injector Offset (B3701) or maybe B4002. Although I am not really convinced to that as it should influence MAF closed loop operation as well. What do you think? Unfortunately I will not have a chance to give it a try as my engine is currently out of the car.

MarcinK

[bink]

Guys, do you have this lean condition on cold SD startups only? I have the same situation but in my case it happens after any startup - also when engine is hot (but the whether was cold at that time) - for the first few minutes.
I tried to find any dependencies but they are not obvious. What I have observed though is that the alternator voltage is higher after every engine start (like >15V) and than gradualy decreases (to 13.8-14V). So I started to thing about Injector Offset (B3701) or maybe B4002. Although I am not really convinced to that as it should influence MAF closed loop operation as well. What do you think? Unfortunately I will not have a chance to give it a try as my engine is currently out of the car.

MarcinK

That's what I had noticed.
My Idle AFR was better (more stable) after I used the correct offset table. (FWIW-low MAP fueling was better also) I use the GTP injectors and the ASA tune has the corrected GM tables.
I have only tuned one car - you guys have much broader experience.

Cheers,
joel

[jfpilla]

MarcinK,
My lean condition, in SD, only happens when the car is started cold. The AFR is exactly 18.62 and if I let it idle to 84C* it will then track Commanded. These numbers are consistantly the same regardless of how I have set the main fueling tables. I looked at logs going back a year. It's real hard to figure since 18.62 is observed, at startup, regardless of IAT and ECT as long as it's 50* and below(the only logs I have). At 80*and over commanded is always used. The immediate tracking of Commanded at 84* is also confusing. It sure seems like something is controlling these changes. I also replaced my battery 2 weeks ago and have not seen any difference. Voltage at start-up varies a lot. It seems to be lower and creeps up slowly when it's very cold out. other times it's right on 12V and goes right to 14.1.
Also, it's not VE's. The same cells produce correct AFR when warmed. As before, I'm lost and will stay with the MAF.
Joe

[WicketMike]

i was reading the thread that marcinc started about a month ago on this same problem and somebody mentionted that maybe the cranking VE table. He said that it is used for a little bit after cranking. does anybody know for how long? and could this be part of the problem?

[bink]

MarcinK,
My lean condition, in SD, only happens when the car is started cold. The AFR is exactly 18.62 and if I let it idle to 84C* it will then track Commanded. These numbers are consistantly the same regardless of how I have set the main fueling tables. I looked at logs going back a year. It's real hard to figure since 18.62 is observed, at startup, regardless of IAT and ECT as long as it's 50* and below(the only logs I have). At 80*and over commanded is always used. The immediate tracking of Commanded at 84* is also confusing. It sure seems like something is controlling these changes. I also replaced my battery 2 weeks ago and have not seen any difference. Voltage at start-up varies a lot. It seems to be lower and creeps up slowly when it's very cold out. other times it's right on 12V and goes right to 14.1.
Also, it's not VE's. The same cells produce correct AFR when warmed. As before, I'm lost and will stay with the MAF.
Joe

Well Joe that completely shoots down my thoughts on Offset - I'll shut up now!!!:muahaha:. NO, I'm not being sarcastic either...just funnin. :D

Cheers,
joel

[deezel]

John,
I don't know if we can assume another table but I sure wish there was a fueling table based on IAT.


My cal has B3633, Initial Intake Temp Enrichment table. However, it is zeroed out in my tune. It is a one-column table of an EQ ratio adder vs initial IAT. I assume this adder is applied until the end of the "initial after-start" fueling algorithm. I would hope that the adder moves along the table (updates with IAT) as the IAT rises to allow a gradual phase-out of the adder as normal operating temps are approached.

[WicketMike]

My cal has B3633, Initial Intake Temp Enrichment table. However, it is zeroed out in my tune. It is a one-column table of an EQ ratio adder vs initial IAT. I assume this adder is applied until the end of the "initial after-start" fueling algorithm. I would hope that the adder moves along the table (updates with IAT) as the IAT rises to allow a gradual phase-out of the adder as normal operating temps are approached.

Paul (Blacky),

is this a hidden table on the 98's?

thanks

[jfpilla]

B3633 is 0'd on the 2003 also. B3632 and 3633 both have (NONE) in the title. What does that mean?
Joe

[Black02SS]

I don't think this has to do with IAT to be honest. I have found that I will see a lean condition if I have been driving the car and then stop it, wait about 5mins, start her up again and it does the same thing with the motor hot.

[Black02SS]

My cal has B3633, Initial Intake Temp Enrichment table. However, it is zeroed out in my tune. It is a one-column table of an EQ ratio adder vs initial IAT. I assume this adder is applied until the end of the "initial after-start" fueling algorithm. I would hope that the adder moves along the table (updates with IAT) as the IAT rises to allow a gradual phase-out of the adder as normal operating temps are approached.
This table as well as the Inital ECT Enrichment are added to the Commanded AFR {B3605} when viewd in EQ Ratios. I did a test just to make sure and I ended up with a commanded afr of 6.1:1..... Here is something else to consider, but I don't think this is the problem. I have seen my timing differ on inital startup for a short period of time from what it is at full operating temps, but once it stabilizes the afr still doesn't match the commanded.

I think there is another table that is based on TIME and it multiplies/adds a factor to lean it out based on VE/MAF table. I don't believe it is something that is controled by the Commanded AFR.

[Black02SS]

Also, it seems that it doesn't matter what you command on startup it always shows lean. I just went back through my log from this morning and checked my Commanded vs. Actual. Seventeen seconds after inital startup, my Commanded was 9.55 vs Actual of 13.72. (This was a test I wouldn't recommend setting your commanded to 9.55) I have another log where I show a 12.08 for commanded vs. 16.05 for actual.... Sorry, just talking outloud... Looks t obe about 4points off from the commaned upon startup..

[GMPX]

Just a thought.........log your injector pulse widths (or maybe just one) GM.IBPW1. Do a cold start and save the log.
Flash the car and give it more fuel for the next cold start in the morning (similar conditions). Observe any difference and take note of the AFR's both times.
Now, alter the IAC so it adds more steps at startup and relog, watch what happens to your Injector pulse widths/AFR with more IAC counts......

Cheers,
Ross

[Black02SS]

Just a thought.........log your injector pulse widths (or maybe just one) GM.IBPW1. Do a cold start and save the log.
Flash the car and give it more fuel for the next cold start in the morning (similar conditions). Observe any difference and take note of the AFR's both times.
Now, alter the IAC so it adds more steps at startup and relog, watch what happens to your Injector pulse widths/AFR with more IAC counts......

Cheers,
Ross
Let me see if I follow you...
1) Log IBPW
2) Add fuel for the next cold start (where? Commanded Open Loop Table)
3)Alter the IAC (B4401?) I have never known how to adjust IAC steps at JUST startup. This table is at 310 for me now as that is the stock value.

[GMPX]

My train of thought and I may be totally wrong because I have not played around here too much (and it's 12:55am), but I am thinking the added IAC steps are causing more air to be consumed and without the MAF the PCM has no way of knowing this. Now shoot me down, but this is only a problem afer starting when the IAC offsets will be greater than normal running?.
My theory on monitoring the injector pulse widths and AFR's is to get base numbers in the log file before adding fuel and after to see an effect (or how much things change). Then going and altering the IAC position tables after a start {B4303} look to the injector pulse widths (are they still the same) and the actual AFR, if you now have more steps, same Injector pulse width but different AFR then that might just mean something.

Cheers,
Ross

[Black02SS]

Hey Ross... I don't have B4303 in my OS. I have B4403 which is the effective area. Remember, I don't know how to properly change the steps in this table. I could just move them down a few places if that is what you are refering to.

[jnorris]

My TB is drilled and I have moved the IAC Effective Area table down between 3 and 5 positions from stock as well as leaving the table stock with little to no difference in the lean problem.
Also keep in mind that if I let the car sit for 15 min or so and restart it the lean condition will be there. If I turn the car off and restart it within 5 min the lean condition will not be there.:nixweiss:

Take a look at this post. There is logged data for the IAC steps. At the time my IAC Effective Area table had the stock values in it.

http://efiforum.iqd.co.nz/showpost.php?p=15692&postcount=27 (http://efiforum.iqd.co.nz/showpost.php?p=15692&postcount=27)

John

[Black02SS]

If I turn the car off and restart it within 5 min the lean condition will not be there.:nixweiss:


Mine does....It may not be as drastic as a cold start, but it still reports lean.

[marcink]

Unfortunately I do not have possibility to check the possible suggestions you are mentioning on this thread, as I will have my car back running probably in March. But please keep the discussion open as someone might finally find a definite solution.
Thanks,
Marcin

[WicketMike]

Is this just a 1998 problem? i know that me and Jnorris have 98's, what about everybody else that has this problem?

[Texas Terminator]

I too have an issue regardless of temperature or time. Speaking of time, i must agree that there is a good possibility that there is another table that we can not see. If my motor dies (regardless of temperature) i still have a lean condition when i try to restart, even if i don't cycle the key.

[vetteboy2k]

I too am seeing the same issue on a 2000 C5 with a 2001 Custom OS3. So it's not just with 98's.

[Black02SS]

Is this just a 1998 problem? i know that me and Jnorris have 98's, what about everybody else that has this problem?
Nope not at all. I have done almost every year and have noticed it on all.

[WicketMike]

Nope not at all. I have done almost every year and have noticed it on all.

What about the people that have a EFIlive custom O.S.? are they having the same problem?

maybe you have to have a EFilive Custom O.S. to not have the problem? :nixweiss:

this really sucks, because the car feels so much smoother in SD. Its like night and day for me. it really helps with my 231/237 cam. I didnt think the car could even be tamed like it is with that cam.

Is there anybody that has done AutoVE w/o having a Custom O.S. and know for sure that they arent having this problem?

[Black02SS]

What about the people that have a EFIlive custom O.S.? are they having the same problem?

maybe you have to have a EFilive Custom O.S. to not have the problem? :nixweiss:

this really sucks, because the car feels so much smoother in SD. Its like night and day for me. it really helps with my 231/237 cam. I didnt think the car could even be tamed like it is with that cam.

Is there anybody that has done AutoVE w/o having a Custom O.S. and know for sure that they arent having this problem?
I've used both, same problem. I actually didn't really notice it until I had the Custom OS, so I switched back to a reg one to see and sure enough, same problem.

[marcink]

I have noticed this problem on my '99 C5 with OS upgraded to 2002.
Would it be possible that the commanded and actual AFR in the cylinders are right and equal but actual AFR is just showing lean at the exhaust? Like secondary AIR system running for the first 240s (4 minutes)?

It seems that this behaviour is only related to time and not IAT, ECT, MAP, battery Voltage or any other parameter, right?

Marcin

[Black02SS]

I have noticed this problem on my '99 C5 with OS upgraded to 2002.
Would it be possible that the commanded and actual AFR in the cylinders are right and equal but actual AFR is just showing lean at the exhaust? Like secondary AIR system running for the first 240s (4 minutes)?

It seems that this behaviour is only related to time and not IAT, ECT, MAP, battery Voltage or any other parameter, right?

Marcin

I totally agree on the time aspect. I know on my car, that I don't even have a AIR pump installed so that sorta eliminates that I think.

[GMPX]

Some tables have just been added that 'might' address this issue. They will be in the next update.

Cheers,
Ross

[jnorris]

Some tables have just been added that 'might' address this issue. They will be in the next update.

Cheers,
Ross

Can you provide a little more detail?

John

[Black02SS]

Can you provide a little more detail?

John
:iamwithstupid: Your holding out Ross.... ;)

[GMPX]

No, I just spent all day doing the changes and adding things, I want to run them past Paul first.

Cheers,
Ross

[Black02SS]

No, I just spent all day doing the changes and adding things, I want to run them past Paul first.

Cheers,
Ross
You take as long as you need. I have found that good things are worth the wait.

[WicketMike]

Some tables have just been added that 'might' address this issue. They will be in the next update.

Cheers,
Ross

Hey Ross,

Is the update for all O.S.? or just the EFIlive custom O.S.?

thanks

[WicketMike]

i did some more messing around today.

I uploaded my old MAF tune the one before i started messing around with SD. I uploaded it but with the new VE tables that i made doing the AutoVE and it was still really lean. So then i put the Backup VE table back to stock and left the Main VE table alone and uploaded it again, now it was ok.
Then i unplugged the MAF and tried the SD again and samething it was very lean, so i put the BackupVE table back to stock and it was running so rich that it wouldnt even idle.

Why would it be ok when you dont touch the BAckup VE table with or w/o the MAF plugged in but only lean when you did both ways.

Is the backup VE table only used up to a certain temp? or something like that or maybe its used with the main VE table? like the octane tables are?

i hope you can follow all my rambling. :-)

[bink]

Wicket Mike - so in both cases when you put your stock "backup VE table" in the afr was stoich?? Are you Open loop with the MAF and SD?

[WicketMike]

Wicket Mike - so in both cases when you put your stock "backup VE table" in the afr was stoich?? Are you Open loop with the MAF and SD?

maf plugged in, stock backup VE table, AFR is stoich during warmup
Maf plugged in, tuned backup VE table, AFR is real lean during warmup

Maf unplugged, SD mode, stock backup VE table, AFR super rich during warmup
Maf unplugged, SD mode, tuned backup VE Table, AFR real lean during warmup

ill test it again tommorow

[Black02SS]

maf plugged in, stock backup VE table, AFR is stoich during warmup
Maf plugged in, tuned backup VE table, AFR is real lean during warmup

Maf unplugged, SD mode, stock backup VE table, AFR super rich during warmup
Maf unplugged, SD mode, tuned backup VE Table, AFR real lean during warmup

ill test it again tommorow
I maybe have missed this, but when you did these tests, what was the commanded afr for each test and the actual? Also like bink asked, were you in open loop or closed? I would like to see this test in open loop.

[marcink]

I do not think this is related to Backub VE table as there is no Backup VE table in the 2002 OS I was using when I had this problem. Although I have a '99 C5 which originally uses this table...

Marcin

[WicketMike]

i just tested it out again today and now its now running lean with the MAF plugged in, but i swear it did yesterday. :-(

i hope we can get the update soon, pulling my hair out :Eyecrazy:

[jfpilla]

i just tested it out again today and now its now running lean with the MAF plugged in, but i swear it did yesterday. :-(

i hope we can get the update soon, pulling my hair out :Eyecrazy:

Try this. Pull the fuse or disable the A.I.R. pump, by tuning and see if it's really only a false reading.

[Black02SS]

Try this. Pull the fuse or disable the A.I.R. pump, by tuning and see if it's really only a false reading.
Mine is disabled all the time. Heck, I don't even have a A.I.R. pump....

[WicketMike]

Mine is disabled all the time. Heck, I don't even have a A.I.R. pump....

i got rid of A.I.R. and egr

[Black02SS]

i got rid of A.I.R. and egr
Shoots that idea.... :muahaha:

[vetteboy2k]

Yea, I don't have an AIR pump installed anymore either. Seeing the same thing at cold start-up.

[jfpilla]

Sounded like such a good possibility. Back to the drawing board. :Eyecrazy:

[hpcubed]

This is probably not the problem. But when you first start the car the air injection pump turns on. So set the air injuection pump "turn on temp" to max so it does not turn on. I was stumped by my lean AFR on start up. When I turn the air pump off, wide band matches commanded.

[jfpilla]

This is probably not the problem. But when you first start the car the air injection pump turns on. So set the air injuection pump "turn on temp" to max so it does not turn on. I was stumped by my lean AFR on start up. When I turn the air pump off, wide band matches commanded.

HP thanks for the info. I didn't try it because the others said they had removed the pump. I started my car today in SD and used the BI-D controls for AFR and it went right to the AFR I set. I turned it on and off a few times and the AFR followed. I also lowered Charge Temperature Blending at 0 and 10 by .12 and that "seemed" to work but I want to see what happens at -7*C IAT startup. I will try turning off the pump after that.


Are those with lean starts using a cold air intake?

[jfpilla]

HPcubed
I programmed out the AIR Pump this morning. That was it for me also. It followed commanded right from the startup. I then put back the pump and it went to 18.65:1. I'm confident that is it for my car. Doubt it would run with the same feel that lean. Glad you tried it. I feel a lot better knowing 18:1 is not at the engine.:cheers:
Joe

[WicketMike]

does this have to do with A.I.R. ? i dont have it and i turned the codes off.

what table are you guys talking about to do the "turn off temp"

would that be the B0203 table? just raise that to 140 ?

thanks

[jfpilla]

does this have to do with A.I.R. ? i dont have it and i turned the codes off.

what table are you guys talking about to do the "turn off temp"

would that be the B0203 table? just raise that to 140 ?

thanks

Did you disable or remove the pump? If so your issue must come from something else.
Yes, B0203, 140*C.

Joe

[Black02SS]

Mine (B0203) is set to 256*F. I don't even have the pump in my car. LOL

[VetPet]

Maybe I have this wrong but isn't the A.I.R. pump used during cold start to inject air into the manifolds in order to get the cats heated up as quickly as possible? The 02 sensors are not in play during this period of open loop operation as I understand it. If this is so, I would definitely expect the AFR's to be leaner than commanded. Does anyone have an AFR reading for a stock engine during cold start? There has to be some enrichment for cold start in order to get the engine started and keep it running. What table(s) are referenced during cold start operation? There's something to be learned from this thread and I'm a newbie trying to expand my knowledge.

:thankyou2: :cheers:

[jfpilla]

Vetpet
The AIR Pump injects air into the manifolds to accelerate burning of the richer fuel created by added fuel for start up, less than efficient burning by a cold engine and the cats not being hot enough to clean the gases emitted. This process probably helps the cats heat up too. As for an Airflow reading at start up, if you have an AIR pump, it will look lean. Mine is 18.62:1, or so, with no MAF. With the pump disabled, it's a mess for a short time and then follows commanded. I don't see any useful A/F #'s before it goes to commanded. It might be my WB 02 is lazy, though. I've had it a while.

Let me add, if the pump is on with the MAF, it should be lean for a bit.

Your not a newbie. No more self deprecation please. Be:coool: .
Joe

[eboggs_jkvl]

If you want to disable the AIR, wouldn't the B0204 set to 1 RPM be the catch all that would work? My AIR & EGR are in the attic and I've put all of the codes to sleep. Would I need to set this to stop the AIR from inducing action in the PCM? Right now, it is set at 2825 RPM. It may be appropriate to set B0205 to 1 too.


Elmer

[WicketMike]

so maybe its lean because i have the COT turned off? does the COT turn on at start up?

[eboggs_jkvl]

so maybe its lean because i have the COT turned off? does the COT turn on at start up?


COT is to protect the CATs when you are running too lean. COT adds gas when you are WOT and start to lean out.

E:)

[curtbriggs]

MarcinK,
My lean condition, in SD, only happens when the car is started cold. The AFR is exactly 18.62 and if I let it idle to 84C* it will then track Commanded. These numbers are consistantly the same regardless of how I have set the main fueling tables. I looked at logs going back a year. It's real hard to figure since 18.62 is observed, at startup, regardless of IAT and ECT as long as it's 50* and below(the only logs I have). At 80*and over commanded is always used. The immediate tracking of Commanded at 84* is also confusing. It sure seems like something is controlling these changes. I also replaced my battery 2 weeks ago and have not seen any difference. Voltage at start-up varies a lot. It seems to be lower and creeps up slowly when it's very cold out. other times it's right on 12V and goes right to 14.1.
Also, it's not VE's. The same cells produce correct AFR when warmed. As before, I'm lost and will stay with the MAF.
Joe

I can't see how a cold engine would hardly run that lean (18+ AFR).
Could it be that the WB is giving a lean reading because of the air injection pump is causing the false reading for the first few minutes until it shuts off.
I removed mine and I don't have a lean start.
Just a thought, Curt

[Black02SS]

I can't see how a cold engine would hardly run that lean (18+ AFR).
Could it be that the WB is giving a lean reading because of the air injection pump is causing the false reading for the first few minutes until it shuts off.
I removed mine and I don't have a lean start.
Just a thought, Curt


I don't think this has to do with IAT to be honest. I have found that I will see a lean condition if I have been driving the car and then stop it, wait about 5mins, start her up again and it does the same thing with the motor hot.

That was my post from earlier in the thread.

[jfpilla]

If you want to disable the AIR, wouldn't the B0204 set to 1 RPM be the catch all that would work? My AIR & EGR are in the attic and I've put all of the codes to sleep. Would I need to set this to stop the AIR from inducing action in the PCM? Right now, it is set at 2825 RPM. It may be appropriate to set B0205 to 1 too.


Elmer

It appears there are at least 5 ways to disable the pump.
If you're concerned turn it off.

[jfpilla]

I can't see how a cold engine would hardly run that lean (18+ AFR).
Could it be that the WB is giving a lean reading because of the air injection pump is causing the false reading for the first few minutes until it shuts off.
I removed mine and I don't have a lean start.
Just a thought, Curt

I reached that conclusion in post #96, after reading HPcubeds'.

[VetPet]

Vetpet
The AIR Pump injects air into the manifolds to accelerate burning of the richer fuel created by added fuel for start up, less than efficient burning by a cold engine and the cats not being hot enough to clean the gases emitted. This process probably helps the cats heat up too. As for an Airflow reading at start up, if you have an AIR pump, it will look lean. Mine is 18.62:1, or so, with no MAF. With the pump disabled, it's a mess for a short time and then follows commanded. I don't see any useful A/F #'s before it goes to commanded. It might be my WB 02 is lazy, though. I've had it a while.

Let me add, if the pump is on with the MAF, it should be lean for a bit.

Your not a newbie. No more self deprecation please. Be:coool: .
Joe

Thanks for the encouragement Joe. Since I haven't gone through the actual hands on tuning yet I can't put myself in the same league as the rest of you guys. I'm just trying to put stuff I've read into the context of these discussions and see if I've understood what I've read. I enjoy these discussions and the different ways that people attack the problem. Many heads are better than just one.

:coool: :beer:

[jfpilla]

Thanks for the encouragement Joe. Since I haven't gone through the actual hands on tuning yet I can't put myself in the same league as the rest of you guys. I'm just trying to put stuff I've read into the context of these discussions and see if I've understood what I've read. I enjoy these discussions and the different ways that people attack the problem. Many heads are better than just one.

:coool: :beer:

I'm impressed by the time and effort you're putting in to learn.:rockon:

[curtbriggs]

I reached that conclusion in post #96, after reading HPcubes'.

Joe, I read your post #50, replied and went to bed, guess I should have stuck around.

[jfpilla]

Joe, I read your post #50, replied and went to bed, guess I should have stuck around.

Nick Williams told me weeks ago that it was probably the AIR Pump. I should have tried it back then.
When HP Cubed posted, it suggested I should try it. It's easy enough.

[WS6FirebirdTA00]

Hey guys,

Has anyone else found a cure for this? I have no air pump on my car so that is not the reason for the lean issue. I reach about 14.6 on cold starts but command about a 12:1-12.5:1. What is really bad is a warm start the car goes really lean. It will read about 17:1 on a warm start and buck like crazy, after a few min of running it all clears up though. Just wondering if anyone has found out more. The cold start can be taken care to not be lean, only problem is if it was commanded richer for a warm start, then when running in normal conditions the car would be way rich.

Mike

[marcink]

Any news on that issue?