Ongoing issue with my car dying when stopping. I had this issue years ago when I originally purchased the car, had it 'tuned', sold the car, previous owner had it at the track a few times then sat for 3 years, then I bought it back. I don't have many details of what happened with the car in the few years I didn't have it.

So, the problem is back. After I had it tuned when I originally bought it, the car ran fine. I took it to the guy that had been working on the car to get it track worthy and he said it was a vacuum leak. 'Repaired' that but didn't get but a few miles down the road and still doing it. Took it back then found the heater core was shot. Knowing that wouldn't be causing the issue, I took it to a performance shop to get the core replaced and have them check out the stalling issue. They said car was done. Talked to the mechanic about the issue and he told me he just noticed(after putting everything back together) that there was a tear in the egr valve diaphragm. Um..not sure why they didn't just replace it but whatever. Said that might have something to do with it. Took it home...still stalling. Replaced the egr valve....still stalling.

Sorry for the long story, but more detail the better usually.

As far as the actual stalling....After driving for a few minutes and I let off the throttle anywhere above 1100 rpm...it dies. (so not necessarily coming up to a stop). If I baby the rpms down to idle using clutch/throttle, it will sit at idle all day long. But bump the throttle up and let it drop....it dies.

Seems both mechanics have no idea what the problem is and I am having a hard time finding what could be wrong surfing the net.

Thanks in advance for any feedback.



1990 Ford Mustang Convertible LX
5.0 with Trick Flow and Vortec Supercharger

 

Tried new IAC valve.....no change.

 

Stop throwing parts at it. Test the parts you find suspect.
If my math is right the car is 23 years old. You no longer can trust rubber parts. I would replace all vacuum lines, pcv valve and lines. I would check the fuel pressure regulator because the membrane might be cracked.
I would check the catalytic converter if it is clogged.
I would test the throttle body position sensor.
I would clean the MAF sensor with CRC maf sensor cleaner and I would clean the throttle body with CRC throttle body cleaner.

I do not know how your modifications affect the idle.

If you search Youtube you will find methods of testing systems and sensors. Testing systems and sensors will save you a ton of money compared to throwing parts at it. How much was the EGR valve, and the IAC valve?

 

The EGR needed to be replaced because the diaphragm was torn. ($70)
The IAC..$60. When I swapped that out, it was worse.
Your suggestions are informative and I will send them to the mechanic looking at the car tomorrow.
I don't have the tools and know-how to keep chasing and change out all the hoses/lines. And I need the car back to running since it is my daily driver for now.

I know I don't have all the info on the car. But the engine was cleaned up and 'bolted' up about 3500 miles ago. Went from the 7-up car to the super 7-up car when the previous owner before I originally bought it 7 years ago sent it off to a performance shop. Granted, sitting in a garage isn't the best thing for lines/hoses, but it wasn't a barn and the car was run/driven on occasion.

thank you for the suggestions.

 

Mechanic says the idle bar was backed out all the way...causing the problem.
Guess I will see when I pick it up.
They recommended replacing the throttle body to an AcuFab? because the one I have is 'known to have problems'.

Hopefully good to go.

 

It is still dying on ocassion. The idle was adjusted and 'catches' most of the time when letting off the throttle. I was told that the throttle body needs to be replaced to completely correct the problem. Currently has some aftermarket one that is 'known' to have problems and was told Accufab has one that is one of the best.
Hoping that will correct the problem..but won't be able to do the swap out for a couple months most likely.

Thanks for the ideas.

 

just a thought did you change fuel filter had one get part clogged almost like running out of gas

 

Yeah..that was changed out when I hadthe first tune.
Seems like throttle body is the culprit. I'm guessing it's going out of adjustment again because it is dying a little more/easier again.
Hooefully next months project.