98 Mustang Gt running issue

[rjbonham]

I have a 98 Mustang GT. This is my problem, I went to leave work today and the car started right up. But died right away. I found that if I keep the RPMS around 800 or better the car runs great. I live about 30mins from work. I was able to get it home by keeping the RPMS at 800 or above. When I got home I put the car in park took my foot off the gas and the car Idled fine. I sure could use some help. Thanks in advance for any advice.

 

[wmburns]

What is the status of your battery? Are the battery terminals clean, corrosion free, and tight?

I'm thinking that the battery and/or the charging system is weak which is allowing power to be interrupted to the PCM. After a PCM reset, the idle trim values need to be re-learned. Which explans why it was a problem at first but then OK after a drive.

In any case, clean the MAF. Check for vacuum leaks.

 

[rjbonham]

The battery is in good shape. Could it be the Idle Control Valve? I will clean the MAF sensor and see what happens. Thanks

 

[wmburns]

IMO think vacuum leak first.

 

[bhuff30]

I think it is very possibly an IAC (idle air control valve) problem. The IAC tends to freeze up and when it does, the engine can't run without additional throttle. If that is the problem, then you can either clean the valve for a temporary fix or replace it.

My IAC is more likely to stick in the winter time and when it does, I have to give the engine additional gas to keep it running. Then, after the engine warms up, it will often idle fine because not as much air is required to keep it running or the valve just randomly starts working again after warming up. Seems to be a fairly common problem on these engines.

 

[rjbonham]

Thanks for the advice. I cleaned the Idle Control Valve and the car started and idled as it should. The inside of the valve looked like it was rusty. So even though it runs fine I think I will replace it. It is so easy to get too.
Again thanks for the help.

 

[LaserSVT]

Was gonna say about 90% of the time a sparadic idle issue is always the IAC. Cleaning it will diagnose the problem but it will return in a month or so, sometimes faster. Good idea to replace it.

 

[bhuff30]

Sounds good. Hopefully, replacing the idle control valve will fix the problem. If not, you took one major piece our of the puzzle.

Thanks for the advice. I cleaned the Idle Control Valve and the car started and idled as it should. The inside of the valve looked like it was rusty. So even though it runs fine I think I will replace it. It is so easy to get too.
Again thanks for the help.