car keeps stalling

[coreyc123]

Ok so i will be driving for about half hour and will put the car in to netural and it will die out.Also some times the car will almost stall but idle around 500 rpm but will stall if i have to wait to long to drive . I wasnt sure what to check sensors, vacum leaks, grounds,etc.Any help would be awsome -thanks corey-

 

[rgeier11]

Some sort of DSM logger would be the first step. Odds are it is your ECU. You can take out the car's ECU and open up the case. If there is burning/fish smell, it is most likely damaged.

 

[chucklesas]

Sounds like an intake leak to me. Check the recirc tube from the BOV and your intercooler pipes.

 

[coreyc123]

wouldnt it be a problem more then when im driving and stoping tho? it wont stall out if i start the car and let it idle

 

Part of the operation of the ISC is what used to be called a "dashpot", a device on the old carb cars that let the idle speed down slowly, instead of dropping like a rock. If the ISC isn't functional, either because the ISC itself is bad or the ECU has issues, the ECU can't "catch" the idle as it drops. The rpm will overshoot the idle rpm, and often stall. There are several things you should check:
1. Open the ECU and make sure the caps have been replaced. Check the ISC driver chips, IC105 and IC107, to see if either of them look burned. Pull the board and look at the bottom side of the board, underneath the 47uF cap, to see if the skinny ISC trace underneath it is still intact. Also look underneath the cap itself on top of the board. That ISC trace is often the first victim of acid leakage from the 47uF cap.
2. Set the idle speed, as per the VFAQ:
click
3. Check your base timing with a timing light, as per the VFAQ:
click
I have found that the ISC has a much tougher time catching the idle if the timing advance isn't at 5* or more.
4. Get a cheap logging setup. The software is free. This will allow you to see the operation of the ISC and the idle-closed switch, among many other things that will have you diagnose issues.

 

[belize1334]

That was happening to me and it ended up being a short on my Vehicle Speed Sensor wiring. The ecu didn't know the car was moving so it was letting the idle dip to low. Then I'd apply the brakes and that'd pull a little vacuum from the manifold and the motor would stall. It used to happen pretty much any time I pulled up to a red light.

There are a few other things that depend on the VSS which can be used as a diagnosis. The one that comes to mind is the variable speed wipers use the vss signal to speed up the wipers. If you put them on the variable setting and then go for a cruise you'll know right away if the vss is working. Also, if you have a two-step launch control setup you can tell that the vss isn't working cause you'll be stuck on 5000rpm rev-limiter (or whatever you have it set at).

 

[prove_it]

We have varible speed wipers that vary with speed? I never knew this. Are you serious? I've never noticed this. Not to hi-jack this thread, but someone please PM and tell me more!

 

[talon]

Vacuum leak tester here