Car dies at idle

[Bmoore04]

A4 98 camaro ls1.
Some of my mods are:
Heads
cam
intake
stall

The car dies when stopped in drive/reverse. After about 15 minutes of driving it will start to idle fine but until then it dies at every light/stop sign.

In the log I posted if you look at the first 30 seconds and then again at 6 minutes you can see the car dieing. Anytime the car isn't dieing it is because I put it in neutral to keep it alive.

If I need to change up my cfg or do anything specific in a log file please let me know so I can get that information asap. Any help would be appreciated.

[Pekka_Perkeles]

I think that the problem here is that the data you have logged doesn't help too much.

As a general rule, when trying to fix idle, you need to log idle-related PID's. In a wider sense, that could include quite many things and of course there's a certain order of things you have to tune, such as getting mixture right. But also things like Desired Idle Airflow and in your case IAC-related PID's will be important, sooner or later.

Ah, one more thing. Even before you drive your car, you can scan (and fix) lot of thigs. Just do a search using these words: russk idle airflow

[Bmoore04]

I think that the problem here is that the data you have logged doesn't help too much.

As a general rule, when trying to fix idle, you need to log idle-related PID's. In a wider sense, that could include quite many things and of course there's a certain order of things you have to tune, such as getting mixture right. But also things like Desired Idle Airflow and in your case IAC-related PID's will be important, sooner or later.

Ah, one more thing. Even before you drive your car, you can scan (and fix) lot of thigs. Just do a search using these words: russk idle airflow

Thanks! This is exactly what I was looking for.

[Ben Charles]

If you don't mind me asking where you located??

[Bmoore04]

New log is up.

The car did not get a chance to get as cold as I would have liked but hopefully we can still make some improvements.

[Pekka_Perkeles]

Ok.

If you look at your log, you can see that the IAC counts is around 130 when the engine is at normal operating temperature. I'm not an expert of cable-driven TB's, so just follow what's been explained here, written by Rinkrat456:

http://www.hptuners.com/forum/showpo...44&postcount=5

Another interesting thing in your log is STIT. It is around -4 grams when idling stationary when the engine is at normal operating temperature. Since your LTIT is zero, this means that the fixed value in your tune, so called RAF (Base Running Airflow), is about 4 grams too high. However, in practice lowering RAF by 4 grams you'd probably overshoot.

Finally, there might be some missing PID's still, which would explain the difference between your RAF and Desired Idle Airflow values. The pic below shows just the basic principle (to my understanding):

[Pekka_Perkeles]

Here's probably useful pic as well.

Arrow number one points the static RAF in a tune. In this case it is 9.40 g/s and does not change by itself.

Arrow number 2 shows what the PCM thinks the engine wants, i.e. Desired Idle Airflow. It is 10.88 grams/sec.

Obviously these two do not match. In perfect world they would.

Arrow number three shows the long term "Idle Air Error", or LTIT. In this case it is a positive value, since the static RAF is too low.

In addition to LTIT, for fans and AC there is a positive value as well, as shown by the arrow number 4.

All in all, RAF + LTIT + Fans + AC create a rather static value for the Idle Air.

In this particular case, RAF+LTIT+Fans+AC = 9.40+2.43+0.10+0.81=12.74 grams/sec.

However, 12.74 is too high, as the engine wants 10.88 g/sec (Desired idle Airflow).

Now, since the RAF is static value, Fans is a static value, AC is a static value, only value that can change in long term is LTIT.

The way how LTIT is changing is based on STIT, shown by the arrow number 5. STIT is dynamic, quickly changing value. If you substract -1.88 from 12.74, it will give you 10.86, which is almost exactly Desired Idle Airflow. In other words, STIT affects the LTIT value. In this case LTIT is too high, and thus STIT is negative.

Whenever LTIT's and STIT's are near zero, everything should be ok. If these values are very high, then problems will follow.