Can anyone take a look at my log file from freescan for my 89 corvette? I am trying to diagnose a stall at idle and there isnt much here

log file

 

Most of the data is incorrectly labelled and/or incorrectly scaled so the resulting values don't make much sense. (Wrong tool for the job, or improper setup)

Maybe 9-10 signals appear to have reasonable values as shown: https://datazap.me/u/tequilaboy/log-...19-20&solo=3-7

Suggestion: use a better tool such as DataCat (free evaluation period, I think).

The IAC counts appear to be pretty high (if the signal can be trusted, but I wouldn't attempt to draw any conclusions from this data).

 

ive been messing with so many useless programs, no problem buying tunercat.... thank so much... see log file link to data cat file

 

That's much better.

Near the end of the log, you can see that it needs around 75 IAC counts in order to idle in gear at or near the target rpm. So about 50% of the available range (160 count maximum) is being used in order to maintain a warm idle. This may be a contributing factor to the stalling.

What is the coolant temperature when it is likely to stall?

 

that drive it didn’t stall next drive it stalled, seems to be intermittent as well, will log again , coolant is 208 or more when it stalls
trying to solve this I did tps,iac,maf but back to original maf, cap , rotor , plus. Coil , now trying cable

 

Here's a limited export of your log showing the IAC behavior as described above: https://datazap.me/u/tequilaboy/apyz...3251-3301-3224

Other signals look fine.

 

so I did another capture or two and got it when it failed... At the time the car acted up it was from a new key cycle, logger was recording, when car stalled got bus failed. When car acts normal even with key off bus is still communicating. The time the car acts up goes from reading to bus failed happened more than once. I wonder if I am loosing connection to the computer or a loose / bad ground somewhere. This may kill me.. but might be on to something ....I really appreciate the help, this is a new IAC or the 2nd new one , these are genuine gm from rock auto. Have any idea? Here is a link to a few more logs , I owe ya a beer or a few dozen for the help and many thanks. new logs link

 

Its on the verge of stalling at the end of the 3rdtime log (and probably did stall just as the recording ended).

https://datazap.me/u/tequilaboy/89-s...rk=95-20-59-73

Note: There is a break in continuity between samples 3314 and 3315. During the time in-between (~45 seconds), I think the IAC has become out of sync with the ecm and is not really fully open as indicated by the logged IAC position (160 counts) from 3315 on. I think it is simply starved for air during this time and the ecm can't open the IAC any further to prevent the stall. This can happen from time to time.

Cycling the ignition is one way to restore synchronization since the ecm will command the IAC through the full numerical range. It will cycle fully open, fully closed and then open again to the intended pre-start position of 160 counts (x -> 255 -> 0 -> 160). You can see the IAC ramping up and down after the ignition is switched off.

In my own car, I have some other methods to combat this issue due to careful adjustment and some custom tuning tricks that allow me to force synchronization on demand.

 

Do you have a suggestion on how I can fix this? A custom tune? a different brand iac? I just drove the car for an hour all was fine, hit a stop light and she died, then every key start same issue here is the log log of it where i had to rev gas let off and she died

 

You can always reduce the engine's dependency on the IAC by adjusting the minimum throttle opening and tps voltage in order to minimize the IAC counts during a normal idle (in gear with hot coolant). When adjusted in this manner, an IAC offset if it should occur may result in a bit of a rev-hang or elevated idle speed under some conditions which is arguably a better alternative than stalling.

If you have tuning equipment, you can play around and force the idle speed up and down to determine if there is a pattern with the IAC sticking in one direction or the other. Otherwise, you can check the wiring connections, coil resistance, try and keep it clean and exercise the IAC often with plenty of throttle application.

With custom tuning, you can increase the IAC numerical range beyond the physical range to give the ecm some more control authority if you should reach the numerical limits (normally 0 to 160).

I will take a look into the latest log.

Update: The latest log is a bit different, but it still shows a similar trend. It won't idle on its own without adding throttle even at 160 counts. Near the end of the log PID control does not even engage as the revs are dropping, so it never even attempts to counter the stall which is a bit strange, but this may be a byproduct of the elevated IAC counts.

If you can get it to idle on its own, try this: while logging data, in a safe manner, manipulate the tps sensor to simulate a half-open throttle without actually opening the throttle to see if the IAC and rpm will react to the tps sensor movement only. The IAC should follow the throttle and the rpm should increase accordingly. We want to verify that increased IAC counts actually result in increased airflow.

 

Just did a smoke test and the throttle body has major air leaks. that is why iac hunted. Thanks for the help

 

How many miles does your car have on that throttle body? I have 128K on mine and have not experienced this issue - yet - and am trying to figure out what age this sort of problem shows itself. Thanks -

 

Strange. One would expect air leaks to raise the rpm, lean the mixture and result in both elevated blm and reduced IAC count readings in order to compensate for the extra un-metered air.

 

I just ordered bbk throttle body should be here in a day or so and will report back. See link to smoke test video Watch me

 

54k, link to video of smoke test https://streamable.com/rs785g
tester was $120 online