Lean Cold Start Problem

[hymey]

Thats correct. Manuals only.

[hymey]

was b0138, cranking enrichment any help?

[swingtan]

Hi Hymey, no that didn't really help at all. I've been playing around with it and have yet to get a definitive fix. I have found the following has had some effect. You already know some of these but others may not....

• B1832: Cranking Idle Air. This controls the amount of idle air for the first 8 seconds after the engine starts. I found that the stock settings in my OS were set very high, resulting in a start up flare and lean spike. Reducing the values has settled the flare right down and helped with the lean spike.
• After flashing in a new tune, bypassing the idle re-lean process seems to help as well. Once the ignition has been off for the 15 second timer, turn it on again and pres the throttle to the floor 5 or 6 times, then switch off again. Now when starting it seems to be a lot better.
• B1041 & B1042:Open Loop Normal Commanded Fuel: both these should help, but I haven't quite worked them out completely.
• B0146: This goes with the previous 2. Again I haven't completely worked out the relationship between the 2. Although the info is that B0146 is simply a multiplier for the EQ factor in B0141/B0142, there is something else involved as the commanded AFR's don't match the calculated values.

It's getting close though.....

[hymey]

Thats no good. So commanding richer settings didnt help in B0138? My troubles are different in that mine has problems when hot. Infact a lot of people are having cold start problems with the e38 and have decided to live with it.

B5141, have you disabled this? Cat light off......

B5116,cold start timing reduction...set these to 0.

B5132....set to 5 or 6 degrees. minimum allowed timing.

If the pcm is sparking after TDC (eg -10 deg BTDC) the fuel/wont ignite causing a lean reading on your WB02. If you set your minimum idle spark to 5 deg BTDC it will ensure the pcm doesnt spark ADTC wasting the fuel/air spark.

Sometimes an overich condition can cause a lean reading on 02 sensors because the mix isnt completely combusted and any spark ATDC wont combust completely at all.

Maybe you have already scanned for spark. My min timing was set to -25 and I do know it has effect as previously it was set to 12 deg BTDC and the low idle correction wasnt working properly.
I have just set it to 6 BTDC myself. I will see how it goes today.

Keep us updated

Cheers

Joel

[swingtan]

OK, I think I've found the problem here.

From the way I'm reading it, it appears that the PID's used in both ...

B0138: Cranking Commanded fuel

&

B1832: Cranking Idle Air

have been swapped over.

Here's my thinking, take a breath because this gets a bit confusing....

B0138 is described as "This is the commanded fuel EQ ratio when the engine is cranking. This table is based on the engine coolant temp and engines last run time (in seconds.)"

So I see this as EQ mapped against "seconds since last run". So the seconds would be counting up when the engine is off. The 2 PIDs used are SAE.RUNTM and SAE.ECT. SEA.RUNTM is described as "Time since engine start"

B1832 is described as "Cranking mode idle airflow."

This table maps EQ against SAE.ECT and the time since the engine started and lasts for 8 seconds.... exactly the same amount of time my car runs lean for. Sounds rather interesting. The PIDs used ate SAE.ECT and GM.RUN_TIME, which is described as "Engine run time".

Now if you log both SAE.RUN_TIME and GM.RUNTM you get vastly different results.

SAE.RUN_TIME counts up in increments of 160 every second after the engine has started and resets to "0" when the engine is turned off to accessory.

GM.RUNTM counts up in increments of 1 every second after the engine has started and resets to "0" when the ignition is turned of and back on again. It also resets is the ignition is turned all the way off.

From this you should be able to see why there are problems with B1832 being referenced against SAE.RUN_TIME. Given it increments in steps of 160, the table will only ever be used for 1 second. Then the count for SAE.RUN_TIME will go well over 8 and the table will not be used. have no idea what will get used in the next 7 seconds, but what ever it is, I think it is what is causing the lean mixtures.

Now if we go to B0138, we can also see that there are problems with the table. As it uses SAE.RUNTM, which only counts up at 1/second and has references up to 43200, this table is going to be used for 12 hours. Way too long to be useful. However, if you swap SAE.RUNTM and GM.RUN_TIME in the 2 tables....

B0138 now is valid for 4:30
B1832 now is valid for 8 seconds.

Have I found a solution to my problems?

Simon.

Edit: I've added a small log file showing the differences. Just display the 2 PIDs and you'll see the difference.

[hymey]

Any ideas blacky, this would solve some of my start problems too.

Joel

[joecar]

Simon, did you pm Paul so he would be sure to see this (point him to post #15)...?

[swingtan]

I have now

I was chatting with Hymey last night and we discovered something interesting though. I had logged the injector pulse width during start up and it peaked very high where I had the lean spike. Hymey has suggested that it's as a result of overly rich mixtures, where the fuel is staying in liquid form. this means the WB will not "see" the additional fuel and read as a lean condition, even though it's actually rich.

So I tried leaning out the initial start mixtures in B0138 to compensate. It seemed OK last night when ECT was 50'c but this morning the car wouldn't start. So I had to richen it back up again for the cold start.

Simon.

[Blacky]

OK, I think I've found the problem here.

From the way I'm reading it, it appears that the PID's used in both ...

B0138: Cranking Commanded fuel

&

B1832: Cranking Idle Air

have been swapped over.

It looks like the link PIDs are possibly displayed back to front in the EFILive tuning Tool. However, the PIDs that EFILive uses to link the scan data with the tuning tool maps is just an EFILive display configuration. It has nothing to do with the internal operation of the ECM. The ECM will be using the correct values - unless the PCM itself has a bug, which is extremely* unlikely.

You can change them yourself in the file:
\Program Files\EFILive\V7.5\Configuration\cal_link.txt
Look for the section name [E38] (or [E67]) and adjust the entries for those tables.

One thing that is wrong is the RUN_TIME incrementing by 160 each second. I think it should be exactly 1 to 1. I'll check into that.

* In the early days, I would sometimes complain that something that wasn't working was probably a bug in the PCM/ECM/TCM code. Of the few hundred times I wanted to blame the PCM, it turned out to be only about 2 or 3 times that a real bug was found in the vehicle controller. Over the years, Ross has beaten this mantra into me: "It is not a problem in the controller, it is a problem with my own code".

Regards
Paul

[joecar]

Simon,

You have, ok...

Cold start needs to be rich, warm start can get away with lean.
So is injector pulse width high due to start mixture being overly rich...?
Hmmm... why is injector spray pooling on manifold/head when ECT is warm...?

Ah... I'm thinking out loud [TOL] about what you said.

Joe