Questions and Answers

Mustang Hot Idle Problem Q. Hello Vincent, I currently own a 1995 Ford Mustang GT. 5.0 V-8 engine with Fuel Injection. I've had the car in and out of the shop for the last six weeks and many parts later, I still have a problem with the car.

Basically, when I start the car (when the engine is hot), the car seems to idle erratically and normally stalls. I had a fuel pressure gauge installed and I noticed on the gauge while this is happening that the fuel pressure increases. The increases are not significant, but seem to be enough to flood the car out.

The dealer has changed the mass air flow sensor, done a full tune up, change the fuel injectors, installed a fuel pressure regulator, changed the oxygen sensors and the list goes on and I still have the problem. What drives me crazy is that the car starts and idles fine when the engine is cold. It only seems to happen when the engine is hot. The car has about 60,000 miles on it.

Can you help?
John

A. One thing that will affect fuel pressure is engine vacuum. If, for some reason, engine vacuum goes too low, that will cause a rise in fuel pressure. So I would make sure engine vacuum is good and steady.

I would suggest they check the Baro sensor if you live in a mountainous area. Ford baro sensors can be kind of slow adapting to different levels. Another possibility is the fuel you are using. All gasolines are not created equal. They have different volatility levels and if your brand has a low volatility then it will stumble or have a hard hot restart. Try switching to a major brand of gas and use the octane recommended in your owners manual.

Outside of that, I don't know what else I can offer you the dealer hasn't done. I would keep a mind open to a new part installed being bad as a possibility also.