Car Stalls While Coasting in Neutral

[FrankeSVT]

Hey guys,


I have a low mileage 03 cobra with the typical mods on it: K&N FIPK, C/B exhaust and pulley. The car was tuned by mail order tune from RWTD from previous owner.

The problem: Whenever I am coasting to a stoplight/stop sign I usually put the car in the neutral and cruise up the light. Recently I have noticed the RPM's fluctuating and dipping down to ~600. Sometimes the car will actually stall. I am thinking a custom dyno tune will solve the problem but I do not have all that much knowledge to diagnose. What do you all think?

EDIT:


MAF was the problem everyone. The car idles and coasts in neutral very smooth now. Glad that it was nothing more than a $6 dollar can of electric cleaner couldn't fix. Thank you for your help!

 

[Blueline]

These cars have been known to have this issue. You can check for any loose connections in the intake tube, air filter MAF etc. Try cleaning your MAF (with the proper MAF cleaner) and your IAC. One of these or a few of these may be your problem. If none of these work, you may want to do any performance mods your planning to do in the near future, then have the car re-tuned. It could also be a tune issue, but no point in paying for a tune just for this if your planning mods in the very near future. Check them then report back. GL!

 

[FrankeSVT]

These cars have been known to have this issue. You can check for any loose connections in the intake tube, air filter MAF etc. Try cleaning your MAF (with the proper MAF cleaner) and your IAC. One of these or a few of these may be your problem. If none of these work, you may want to do any performance mods your planning to do in the near future, then have the car re-tuned. It could also be a tune issue, but no point in paying for a tune just for this if your planning mods in the very near future. Check them then report back. GL!

Very good information! Ill go check out those things and post afterwards. Thanks.

All you guys who are running mail order tunes, have you ever had this problem?

 

[TVSCobra]

These cars have been known to have this issue. You can check for any loose connections in the intake tube, air filter MAF etc. Try cleaning your MAF (with the proper MAF cleaner) and your IAC. One of these or a few of these may be your problem. If none of these work, you may want to do any performance mods your planning to do in the near future, then have the car re-tuned. It could also be a tune issue, but no point in paying for a tune just for this if your planning mods in the very near future. Check them then report back. GL!

This.

Sounds like a tuning issue or a jammed/defective Idle air control valve.

 

[vettez062002]

Take the iac off and clean it out. Also map on it with a small hammer. Usually the plunger gets stuck from carbon.

sent from Droid incredible

 

[vettez062002]

Also check for a vacuum leak

sent from Droid incredible

 

[mrose75]

Could just be the tune. Stock tune had that issue. Ford reflashed them to fix it. But my tune is an old RWTD tune and they took care of that for me. Unless they goofed on your tune, I doubt that is it. Good luck and post up your results and let us know what the culprit was.

 

[Bruha]

It is in the tune

 

[FrankeSVT]

It is in the tune

That is what i think as well but i want to clean the MAF first and decide what to do from there. My friend thinks that if it was the MAF my check engine light would be on, so to those of you that have had to clean your MAF, did your check engine light come on?


Here is a great write up for anyone wanting to go ahead and clean their MAF Cleaning the MAF

 

[haskett]

I don't want to hijack this thread, but this might be related.... Sometimes when I jam the brakes real hard, the engine dies. I guess it's dumping a bunch of air into the intake from the booster and killing the motor???

I had this happen to me at the open road race this past weekend when I was diving into a turn at triple digits and it wasn't fun.

 

[Quagmire]

Its either your IAC or MAF. Run the car and unplug the maf if the car dies your iac is bad. then check the voltage across it, just to make sure.

 

[Parts-is-Parts]

IAC Transfer function values need to be increased. Simple.

 

[Satyr]

When this happened to me (other way around, my idle was too high), it was the IAC. You can measure the voltage across it to see its operation value. IIRC, it sweeps between 0-5V.

 

[03cobra#694]

I don't want to hijack this thread, but this might be related.... Sometimes when I jam the brakes real hard, the engine dies. I guess it's dumping a bunch of air into the intake from the booster and killing the motor???

I had this happen to me at the open road race this past weekend when I was diving into a turn at triple digits and it wasn't fun.

Don't think that could be it because it's a hydro boost system and not vac. Please correct me if I'm wrong.

 

[haskett]

When this happened to me (other way around, my idle was too high), it was the IAC. You can measure the voltage across it to see its operation value. IIRC, it sweeps between 0-5V.

Interesting. Now that you mention this, it occurs to me that my idle will occasionally jump up to around 1200. Sounds like I need to look at my IAC!

Thanks for the replies. I will post results.

 

[haskett]

Don't think that could be it because it's a hydro boost system and not vac. Please correct me if I'm wrong.

I think you might be right. I'm showing my age.

 

[FrankeSVT]

MAF was the problem everyone. The car idles and coasts in neutral very smooth now. Glad that it was nothing more than a $6 dollar can of electric cleaner couldn't fix. Thank you for your help!:beer:

 

[03cobra#694]

^^^Thanks for posting the results and cure. :beer:

 

[john3883]

yeah had same issue time to time with stock tune. get retuned with pulley!

 

[Blueline]

:thumbsup:

Glad it worked, cheap fix!