Suddenly lean???

[hquick]

What would cause my tune to suddenly go from almost spot on to about 3-4 points leaner (AFR) across the board?
Can't think of anything I did to cause this. I logged all of my O2's just to make sure my WBO2 hadn't gone bad....but the results seem to verify what the WBO2 is telling me.
I didn't notice any particular issues with the truck's driving.
I was thinking exhaust leak before th O2's but it would have to be on both sides which is just too much of a coincidence.
I cleaned and re-dialled in the MAF for the moment...so it seems to be OK'ish now, but it was damned near perfect before and the MAF shouldn't have needed to be touched.
Any thoughts?

[ChipsByAl]

Were by any chance your fuel trims reading positive @ WOT in the past? If the weather changes and the trims go negative, the PCM would not still be adding the excess fuel to keep the mix where you want it @ WOT.
Al

[hquick]

Well....I usually don't log the trims because I'm running OLMAF. MAF is set at 1500rpm so as to try and catch the lean tip in issues.
We haven't had any major weather changes between the tune being very good to all of a sudden garbage.

[swingtan]

Hi Howard,

Tuesday was a scorcher and the change may have upset something. I'd firstly try a PCM reset to ensure no trims are being stored. Then check what the IAT's were when the lean-out occurred as you may have reached a point you had not seen before.

Simon.

[hquick]

Thanks for the reply Simon.
This started last week before the stinking hot weather.
I cleared all learned trims...that I know of.
So far I've re-fitted the MAP sensor to make sure of no leaks and changed the MAF for a brand new one (I had in the shed).

[hquick]

OK...a bit of a follow up.
I solved the problem.
Seems during the last update....which I downloaded just before this issue started, I somehow ended up with an issue in one of the .cax files relating to transient fuelling.
Well...yesterday I was looking into the 0411 4x4 COS issues a few of us seem to be having and I downloaded the .cax file which allows switching of 4x4 and platforms. When I opened my tune....alot...actually most of the transient tables/parrameters were 'out of range'.
I reset them to how I had them prior to the lean issues I experienced. I also reset the MAF table and everything was back to normal.
Thanks for your help guys.
Let this be a lesson to everybody to ALWAYS check/take notice of the 'OUT OF RANGE' tab.

Just for interests sake....if anyone wants to see the cause of this issue.
Compare these two files.

[Stealth97]

Glad to hear you figured it out!

[hquick]

Thanks Eric.
Actually....yesterday it went south again!
No idea what happened. It was spot on after I reflashed with the fixed out of range parameters.
I drove around all day....no issues.
Next time I started it and drove to work.....up the creek again!
I'm wondering if I'm getting dodgy fuel. Last night it was so lean it was pinging badly.
re-adjusted the MAF table and it's fine again????
No idea at present...haven't had much time to look into it.

[Stealth97]

Sounds very interesting. Let us know what comes about! Let us know if it goes haywire again. I'm real interested.

[hquick]

OK....didn't realize a small change in B4307 "desired airflow" would make such a large difference to the AFR. Seems it is the case.
For the moment I've gone back to OLSD to double check my VE tables.

[hquick]

Well....I don't get it.
One day it's fine...the next it's running full lean.
Yesterday leaving work...I put all of my previously adjusted idle/startup settings back to OEM just to see if the airflow setings were the issue.
My PLX WBO2 was showing 19-20 AFR as I was lightly cruising.
I just thought....what the hell...I'm driving this thing home as is. If it grenades....I'll build that stroker I've been planning.
Anyway...it ran fine with the PLX showing 'LEN' (lean). No KR...everything went fine.
Now I just need to find out WHY????
I've checked the WBO2 against the NBO2's and all report same conditions so I'm stumped. Only thing I can think of is those stupid bloody 'donut' exhaust gaskets.
Any idea's?

Thanks

[joecar]

Howard,

Those donuts don't leak unless they have been overtightened and/or reused too many times...

Do you have the 3 bolt or 4 bolt flanges...?

[Aloicious]

Howard,

Those donuts don't leak unless they have been overtightened and/or reused too many times...

Do you have the 3 bolt or 4 bolt flanges...?

they should be the 3 bolt flanges, I've had mine leak before, just needed some tightening, although I wasn't reading 20+ afr, I was only ~ 15-16 with the leak, ~14.7 after it was fixed. so unless you've got a massive leak, or like the donuts AND header gaskets are leaking, I really don't know. how far was your drive with it that lean? was it lean at 20+ the entire way? how was your ECT?

possibly check your IFR table and make sure it didn't get changed or something with your last pcm flash...

[hquick]

Drive was about 20km's. I trhought it wouldn't run if it was that lean?
Joe, I have the 3 bolt flanges which I checked for tightness last week.
Maybe it's the header gaskets.
All other sensors were showing normal. IAT's, ECT's, EGT's etc...

[hquick]

Here's my current tune and the 'lean' log.

[Aloicious]

Drive was about 20km's. I trhought it wouldn't run if it was that lean?
Joe, I have the 3 bolt flanges which I checked for tightness last week.
Maybe it's the header gaskets.
All other sensors were showing normal. IAT's, ECT's, EGT's etc...

was it stumbling/bucking/lean missing at all durring the drive? I would think that it probably wasn't actually that lean, either exhaust leak or some kind of W/B malfunction or something.

[hquick]

It ran fine....so I'm also leaning (yeah..pun FULLY intended) towards an exhaust leak.

[joecar]

Howard,

A thought cross my mind (what's left of it :D) as I looked at your log...

wideband afr shows 19+... i.e. free air... it might not be a leak (altho do check), it might be the wideband failing/failed...

(this just started happening out of the blue, right...?)

Joe

[Aloicious]

Howard,

A thought cross my mind (what's left of it :D) as I looked at your log...

wideband afr shows 19+... i.e. free air... it might not be a leak (altho do check), it might be the wideband failing/failed...

(this just started happening out of the blue, right...?)

Joe

I was thinking this as well, especially since a constant 19+ afr is a pretty massive exhaust leak....although he did mentioned that he checked the wideband against the narrowband output and they're both showing the same condition:


....I've checked the WBO2 against the NBO2's and all report same conditions so I'm stumped.....

However, you've been running in fully OL for some time now, right Howard? if thats the case, one could argue that its possible that the NBO2's are also bad... (although unlikely both are bad, it is possible, especially if he's been running OL only for a while and not noticed the NBO2's going out.)

another possibly scenario is that there is a wiring problem, perhaps the ground for the WBO2 and NBO2's has a fault of some sort?

[hquick]

True...I have been running OL for a year or more.
I do quite often get NBO2 DTC's so they could all be bad I guess.
I might grab a new WBO2 sensor and check it. Is there a way to clean O2's?
Any idea's on best place to pick one up?

[Aloicious]

True...I have been running OL for a year or more.
I do quite often get NBO2 DTC's so they could all be bad I guess.
I might grab a new WBO2 sensor and check it. Is there a way to clean O2's?
Any idea's on best place to pick one up?

your PLX runs the bosch wideband sensor like the LC-1, right? I don't know where to get one but it should be fairly plentiful I would think. if you've been getting NBO2 DTC's I'd guess they may have already been bad and your wideband just happened to go out too.

[5.7ute]

True...I have been running OL for a year or more.
I do quite often get NBO2 DTC's so they could all be bad I guess.
I might grab a new WBO2 sensor and check it. Is there a way to clean O2's?
Any idea's on best place to pick one up?

Hi Howard.
For the wideband sensors I go directly to bosch australia for mine. Part no 0258007057
These suit my lm-1 but I am not sure if the plx uses the same plug or not. If these will suit I can arrange one for you on my account to save you a few dollars.
FWIW when my wideband sensors have failed at first they have pegged lean under acceleration when the exhaust flow is high, but read fine while idling. Eventually they pegged lean constantly.

[hquick]

Thanks Mick. Actually...that description of failing WBO2 sounds pretty much spot on.
I'll get some part numbers and send you an email.
Thanks again

[hquick]

Apparently it's called a Bosch LSU4.2 type B

http://www.plxdevices.com/products/accessories/boschsensor/

And I just found another site which varified the LSU4.2 is the part number you quoted above Mick.

[5.7ute]

Apparently it's called a Bosch LSU4.2 type B

http://www.plxdevices.com/products/accessories/boschsensor/

And I just found another site which varified the LSU4.2 is the part number you quoted above Mick.

That part number is for the connector with one round end, which I believe is the type A. It is not a very good pic of the connector on there site.
Does anyone have the bosch genuine part number for the square connector?

[playtoy_18]

Could you maybe have an intake leak that is not always open?
3 sensors going bad the same way at the same time just sounds funny to me.
Have you done basic diagnosis yet for tech stuff howard?
I know more than likely you have,just cause your you :D
PCV issue? maybe IAC going goofy?intermittent?
Had both fail before in weird ways that couldn't be diagnosed easily,even looking at PIDS during event.

[joecar]

playtoy_18, welcome to the forum...:cheers:

[Aloicious]

Could you maybe have an intake leak that is not always open?
3 sensors going bad the same way at the same time just sounds funny to me.
Have you done basic diagnosis yet for tech stuff howard?
I know more than likely you have,just cause your you :D
PCV issue? maybe IAC going goofy?intermittent?
Had both fail before in weird ways that couldn't be diagnosed easily,even looking at PIDS during event.

hey bro, welcome...yeah, I agree, 3 sensors all out is somewhat unlikely, however, if his wideband was reading correctly and he was actually running at 19+ constantly from an intake leak, or whatever, it wouldn't drive 'just fine' as he said it was. plus he hasn't used the NB O2s for over a year and they're throwing codes, so the probability of the Wb going out with already bad NB's is higher.

[playtoy_18]

playtoy_18, welcome to the forum...:cheers:

Howdy :D
Alocious and howard and a few others already know me (been with TCII for a few years)
I'll post up a noob thread :fluffy:

[Aloicious]

Howdy :D
Alocious and howard and a few others already know me (been with TCII for a few years)
I'll post up a noob thread :fluffy:

noob post 'eh? I'll see your noob post and raise you the standard reply to noob posts...
USE THE SEARCH BUTTON....
heh
seriously though, good to have you over here man. have you converted to EFILive?

[playtoy_18]

Just received V2 this weekend,plan to attend EFILive class in March.
Have nothing to tune with it yet :( But plenty of use with the scantool.
Haven't got a chance to try it out yet though,need to get some playtime before class-might just buy a truck or car to play with till my project is done.

[hquick]

Hi Ed.
Yeah....I was thinking headewr gaskets or 'donut' gaskets but what Mick described as the symptoms of his wideband playing up....I've seen the same thing with mine.
I'll try swapping out the sensor and see what happens ('cause it's easiest..Lol!).
Jez....I know you're lurking..the answer is still NO!!! I refuse to burn it. Lol!

[hquick]

Here's some pic's of the PLX sensor and it's connector.
Any idea where to get a spare or is it a PLX only thing?

http://img.photobucket.com/albums/v35/hquick/P2100002.jpg

http://img.photobucket.com/albums/v35/hquick/P2100003.jpg

http://img.photobucket.com/albums/v35/hquick/P2100006.jpg

http://img.photobucket.com/albums/v35/hquick/P2100010.jpg

http://img.photobucket.com/albums/v35/hquick/P2100016.jpg

http://img.photobucket.com/albums/v35/hquick/P2100018.jpg

[5.7ute]

Hi Howard.
The part number on that sensor 12575657 is a good number. If you do a quick search with that number it comes up exactly as the one you have in the pic. I will give my suppliers a call in the morning & see what I can come up with.
Cheers Mick
Here is a link http://www.bmotorsports.com/shop/product_info.php/products_id/534

[hquick]

Well....got the new sensor and installed it. No different!!!

[jfpilla]

Howard,
That degree of lean happens with intake manifolds leaking.
It seems to go leaner as your car warms up. Something warping?
I see that you have disabled the AIR pump, but for kicks, try lowering B0204.
Just throwing out any ideas. "I feel your pain" with a hard to diagnose issue.
Joe

[hquick]

Thanks Joe....I'll give anything a try at this point.
There is no airpump installed on this vehicle...does that make a difference?

[jfpilla]

Howard,
If there's no AIR pump ignore that part of what I suggested.
I hate to see you go through this. I've had some frustrating situations, but they always get resolved.
Joe

[Aloicious]

Well....got the new sensor and installed it. No different!!!

dang, that sucks man, I still believe that if its running good and without issues that its not actually running at 19+AFR. check your PCM and wideband grounds maybe? if you're using a common ground point for the wideband and narrowbands, and it has come loose or something, perhaps that is the culprit?

maybe look/feel around the head/headers to see if you have leaks there?

[hquick]

I just changed the throttle body back to the older one. Still no change (clutching at straws here).
I have been using the same gasket over and over....is that an issue?
Here's a small log.
Can anyone tell me if the NBO2's are reporting the same lean condition as the PLX WBO2?
The PLX 'box' seems very hot.

[hquick]

What's considered 'normal' for narrow band O2's and how can I relate the NBO2 logged values to the WBO2 values to know if there is an issue with the WBO2 unit?

[Aloicious]

What's considered 'normal' for narrow band O2's and how can I relate the NBO2 logged values to the WBO2 values to know if there is an issue with the WBO2 unit?

remember a N/B runs on a 0-1v range. your log is showing a pretty consistant 0.8-0.9v, pretty high, and it doesnt seem to fluctuate much, even when the WB is reading in the low 14's all the way up to the 19+, your NB's stay right around .8-.9v, which is lean (at stoich, and in CL, they should be switching back and forth right around 0.5v, or a little lower, yours aren't really switching at all, but then again you're in OL I believe). but if they don't change, even with the WB changes than I'm not sure if they can be trusted. then again it may be the WB that is wrong.

you might try turning CL back on, the O2's will start dumping fuel in for the trims at these lean spots, if you're actually running lean (i.e. intake leak, etc.) it SHOULD run a bit better than it is now, and the WB readings should become a little more consistant, however if you're not actually running lean, (i.e. exhaust leak or something) it should in theory run worse than it is now with the extreme richness, or at least make your exhaust reek of fuel. plus you could see if it changes the WB output any or not....thats an idea at least...that is if your NB o2's are actually working correctly.

sorry bro but I don't know what more to do about it.

[Aloicious]

here's an old log of mine from when I was running CL, you can see the NB switching going on and it averages right around 0.5, stoich.

[hquick]

I've been reading Greg Banish's book 'engine management - advanced tuning' and it shows that stoich is around 950mv. Leaner is below that and rich is above 950'ish.
So....if that's correct....my NBO2's are correct and my wideband is way off???
I recently tucked the PLX 'box' up under the dash to 'neaten' things up a bit in the cab. Thinking back....this issue may have started not long after that and when I pulled it out from behind the dash today it was 'VERY' hot to the touch. I'll try letting it hang in the air tomorrow and see if there's any difference.


For most sensors, anything around 400 - 600mV can be classed as stoichiometric mixtures, which is fine for idle and all light load cruising. Under load, anything less than 600mV will be bad news - too lean. Instead, you want to see voltages which are at the top end of the voltage scale - whatever that is for the particular oxy sensor you are using.

EDIT: I may have interpreted the diagram in GB's book incorrectly. I believe stoich is considered to be 450mv.

[Aloicious]

I've been reading Greg Banish's book 'engine management - advanced tuning' and it shows that stoich is around 950mv. Leaner is below that and rich is above 950'ish.
So....if that's correct....my NBO2's are correct and my wideband is way off???
I recently tucked the PLX 'box' up under the dash to 'neaten' things up a bit in the cab. Thinking back....this issue may have started not long after that and when I pulled it out from behind the dash today it was 'VERY' hot to the touch. I'll try letting it hang in the air tomorrow and see if there's any difference.



EDIT: I may have interpreted the diagram in GB's book incorrectly. I believe stoich is considered to be 450mv.

I've got that book too but haven't looked at it in a while. unless I'm mistaken stoich should be around 450-500mv, and if you look at a stock tune, the O2 swtich points (stoich points) are typically in the low to mid 400's which I believe the factory sets low to be on the rich side for safety. remember that Banish is a Ford tuner, and their O2 wiring and setup may be different than GM's. either way, your O2's SHOULD be cycling up and down around a point and not as flatlined as yours are reading.

you may want to find another PLX user or contact PLX directly to see if the heat is an issue, it seems kinda strange to me, hopefully it didn't fry some of the circuitry or something. (although your log didn't look horrible, there were definantly some questionable lean areas, but a decent amount of the log was fairly close to stoich.)

BTW OT, I may have found some help with the problem we were discussing a while back about the difficulty starting, and the need to feather the throttle while cranking. I don't want to shoot this thread way off course so if you're interested send me a PM, or we can start another thread or something. I just thought you may be interested in it.

[hquick]

I believe I solved the issue!
I'm getting really sick of taking 3 steps forward then 10 backwards. Lol!
Anyway...I think it's the power jack in the PLX 'box'. I had it hanging out of the dash and just took a two hour drive to pickup a set of fender flares I won on ebay (AUD$200...brand new. That's around USD$150 I guess. Dealer here wanted $1800.00). Whilst driving with it steady on around 18 AFR I played with the PLX 'box' and it immediately went to 14.5 or so. As I wiggled the power in connection it went rich/lean/rich/lean.
Might remove that connection and solder a 2 pin plug/socket setup in there instead.
Thanks for helping everybody.
Sometimes it's a simple fix but it may only appear to someone elses eyes.

[5.7ute]

I believe I solved the issue!
I'm getting really sick of taking 3 steps forward then 10 backwards. Lol!
Anyway...I think it's the power jack in the PLX 'box'. I had it hanging out of the dash and just took a two hour drive to pickup a set of fender flares I won on ebay (AUD$200...brand new. That's around USD$150 I guess. Dealer here wanted $1800.00). Whilst driving with it steady on around 18 AFR I played with the PLX 'box' and it immediately went to 14.5 or so. As I wiggled the power in connection it went rich/lean/rich/lean.
Might remove that connection and solder a 2 pin plug/socket setup in there instead.
Thanks for helping everybody.
Sometimes it's a simple fix but it may only appear to someone elses eyes.

Good work Howard. Glad to see you got it sorted. Have you worked out if Jezza might have sabotaged that plug to burn the truck for you.:secret::grin:
Edit: This also proves delco's point about ensuring your wideband has a good, steady voltage source.

[jfpilla]

Nice, glad you got it. Some of the guys were on the right track with their thoughts.:grin:

[hquick]

Thanks again guys.
Mick, I was keeping an eye out for Jez...didn't see any Ninja sneaking around here. Lol!
Yes Joe....it just seemed to me that the NB's were not reporting the same as the WB.

[Aloicious]

righteous, good find Howard!

[joecar]

Good job Howard...:cheers: