99 GT will not idle

[ky99gt]

I have a 99 GT with 103K miles, no modifications. It will crank and run as long as I keep giving it gas, but when I take my foot off of the pedal, the car dies. I have a check engine light, had it checked, said something about the emissions. Will bad O2 sensors cause this problem? If so, which ones to replace, before or after the cats? Thanks for the help!

 

[jstreet0204]

we'd need to know the code just because it said emissions deosn't mean it is o2 related.

 

[RedDaemon]

ever replace the IAC?

who told you it was emissions?

check engine light? interesting, doesnt mean thats the only thing wrong, tho

 

[9musTang9er]

clogged fuel filter? mine did this once

 

[Kurgan]

I would put my money on the IAC valve.

 

[madmatt]

IAC for sure.

 

[the98stang]

^^not for sure, but a possibility. You need to get that code pulled! It wouldn't pop up if there wasn't a problem.

Until you get the code you can try cleaning the IAC, and looking for vac leaks or cracks in the intake manifold. That would be a great start.

 

[NPIGT]

I am having the same problem but I dont have a check engine light on. I also was told the IAC. Also change the fuel filter and plugs, both of those made a great difference in mine. But I still need to change the IAC still.

 

[Mike97gt]

I have a check engine light, had it checked, said something about the emissions.

Pull the codes again and this time write down the exact code numbers. Most likely the problem is a bad IAC but you never knoe if you have a whole bunch of circuit faults then you might have a blown fuse.

 

[fastangboi]

Why do IAC's go bad. This is a real common prob for the modulars. Is it oil from the pcv valve? i have already done the oil separator, so am i safe?

 

[MBDiagMan]

I personally would NOT put money on the IAC at this point in the diagnosis. The problem you describe WREAKS of a vacuum leak. There are some vacuum leaks that do not appear as vacuum leaks such as a leaky EGR valve.

Pull the code, write it down, post it here and in the mean time, connect a vacuum gauge, have an assistant start it up while you observe the gauge. Have the assistant slow the engine gradually and note the vacuum reading at the time that the engine dies. Post the results of that test along with the code.

 

[Kilgore Trout]

MBDiagMan always says vacuum leak when everyone else says IAC...

Just saying...

//in no way am I making fun of an ASE Master

 

[blacksheep-1]

pull the IAC, clean it out real good with carb cleaner, put it back on and see if it helps. If so, then the problem's over, if it helps some, but not much, replace the IAC. they get munged up pretty bad, the one in my F150 was finally replaced at 175,000 miles. I had cleaned it out a few times before it finally died. You may also want to pick up a cheapo code reader, I keep one in the trunk of my mustang. I live in FLA (sea level) and occasionally drive to my parents in the Smokey mountains (not sea level) the car always throws a code about Atlanta, coming and going.