Tech question

[Jhussey1280]

Hey guys and gals. Forgive me if this has been asked before. I searched the forums but couldn't find what I was looking for.

I need some help with a starting issue. Whenever it's really cold outside, anywhere below 25 degrees, my mustang just doesn't want to start. After a few tries it usually fires up and runs the rest of the day. Well a couple of weeks ago we had a cold wave in the teens and the same thing happened only now the car will not fire at all. It cranks, cranks, cranks all day long, and as long as the throttle is held it will stay running, but as soon as the throttle is released my baby sputters and stalls. The battery was just recently charge, but it does feel week still (it's 5 years old anyway). Any idea what it could be? I've been told it's the IAC or the TPS, but I have a hard time dropping money on parts with out 100% confirmation.

Any info you guys can give will be greatly appreciated.
Thanks!

 

[hotpony]

Try unplugging the MAF sensor and starting the car. When you say "throttle is held", do you mean all the way to the floor? TPS can be checked by using a voltmeter and testing for ~.5-1V at closed throttle and ~4-5V at WOT. What year is your vehicle? IAC valve can be removed and cleaned with any type of Carb cleaner or Brakleen, if taken apart, you can inspect for proper operation. Some people opt to remove the IAC completely and adjust their throttle stop, however, this will not allow the engine to "idle up" when the A/C compressor turns on, so you will have to account for this with a higher idle RPM (~800-1000)

 

[Jhussey1280]

It's a 98 GT. By Throttle held I just mean alittle pressure on the pedal, doesn't have to be WOT. could be just holding the RPMS at idle. Thanks for the tips.

 

[wmburns]

Sure sounds like the IAC isn't working. The black vent IAC needs to open to air to provide enough air to start the motor.

However, a vacuum leak could also cause this.

Perform the basic functional tests called out in the following post and let us know the results.

http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649

 

[Jhussey1280]

Thanks so much for that link. It really helped. After following the steps and a few more diagnostics it was in fact the IAC. Thanks a million guys for all the help!