SD newb question

[Pfadt Racing]

I have been running my 99 C5 (422 ci, 540 rwhp) with custom OS 3 in a 2001 software base. I did the AutoVE tuning on the car and decided to leave it in SD mode (nice to not have the MAF in the intake). This is a dedicated race car. The car runs great and makes great power, but has some odd driveability and idle issues.

I didn't make any changes to the software to return it to 'functional' after the VE tuning. Are there any fuel trims that need turned back on or any other features that I need to re-enable?

One of the annoying symptoms I have is that the car will start right up at crank, and idle perfectly. After about 1 to 2 minutes, it shuts off like someone turned the key. It also will not return to idle from a free rev, it stalls almost every time. I can make the idle better or worse with the airflow tables, but never make it return to idle. I have a friend with the same cam that uses all the 01 Z06 cals (same base cal as me) in the idle and has no problems with idle. This has the 90mm TB (as does my friends car).

Another question is, how do I do the crank learn? I have no codes other than that and the learn procedure button is still greyed out in the toolbar. Not all that important, but just wondering if that could cause any of my problems.

Any help is appreciated.

thanks,
Aaron Pfadt
Pfadt Race Engineering
1525 S. Gladiola Rd.
Unit #1
Salt Lake City, UT 84104
888-972-2464
801-386-5148 fax
aaron@pfadtracing.com
www.pfadtracing.com

[ringram]

Sounds like you need to do desired airflow tuning.
If you leave it as it was from autove you will be in open loop speed density. Quite a few guys leave it there, as it gives the tuner the most control over fueling. Well the open loop part anyway.
Do a search on idle tuning, you might need to add more/less air once ECT starts warming up.

[Pfadt Racing]

Sounds like you need to do desired airflow tuning.
If you leave it as it was from autove you will be in open loop speed density. Quite a few guys leave it there, as it gives the tuner the most control over fueling. Well the open loop part anyway.
Do a search on idle tuning, you might need to add more/less air once ECT starts warming up.

I would agree with you, but it is not coolant temp related. The start and idle for a while issue is unrelated to it being cold or hot. It seems like a timer or something. Like some mode that it exits or enters based on time alone.

I have found a very nice write-up on idle tuning and tried most of the 'tools' in it, but still have major idle problems.

thanks,
Aaron

[mjcari]

Aaron,

I can only speak for DCX, Siemens and Bosch controls, but in general during start up (open loop) extra air is injected to overcome startup friction. It is soley a function of time since start, with an initial value determined by coolant temp. On the fuel side, if the engine is equipped with an air pump (which many are today) extra fuel is also injected as long as the airpump relay is active (Run the engine rich - easy start, and the burn off the extra fuel in the catalyst with secondary air. This also lights the catalyst off qucikly and warms those O2 sensors.) Email me, or call me and I'll try and trouble shoot for you. BTW, speed density is the way to go over MAF.

Mike
mcari@dental.temple.edu

[Kevin Doe]

Are you getting any codes? I was getting a P0106 code, and it would shut my car off after about 3 or 5 minutes of idling, just like someone turned the key off. I traced it back to a problem with the MAP values being outside the expected map values. The PCM does a check to make sure the MAP values are in range, there is a max and a min table. I had to move the max table out of the way a bit. No more shutting off.

[Pfadt Racing]

Are you getting any codes? I was getting a P0106 code, and it would shut my car off after about 3 or 5 minutes of idling, just like someone turned the key off. I traced it back to a problem with the MAP values being outside the expected map values. The PCM does a check to make sure the MAP values are in range, there is a max and a min table. I had to move the max table out of the way a bit. No more shutting off.

Kevin,

That is a good thing to check. I very well might have that code. I kind of stopped looking at codes because the behavior is consistent and the light is always on. I'll look into that.

Thanks,
Aaron