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Discussion Starter #1
Hey all, new to the Forum. I have a totally stock (sorry) '02 Mustang GT convertible, about 32K miles, but I'm having trouble finding someone who actually knows anything about it (my dealer included).

My problem is that sometimes when it has rained all day (high humidity?) I will go to start the car and it will start fine, idle at 1,000 RPM like normal starting for a half second, then die. It starts absolutely fine, and I can keep it running with some gas on the pedal, but it just won't idle, that is until it warms up (10-15 minutes of keeping it going with the pedal). Any ideas what can be amiss here?

I called my dealer, and explained the situation in detail, they said that it could be an idle valve, but need to run the diagnostic ($75, 1.5 hours) to check. I bought a Haynes manual, but the only things there are loose vacuum hoses, EGR or PCV problem, clogged air filter, but which one would be related to engine temp and weather conditions?
 
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purduechuck said:
Hey all, new to the Forum. I have a totally stock (sorry) '02 Mustang GT convertible, about 32K miles, but I'm having trouble finding someone who actually knows anything about it (my dealer included).

My problem is that sometimes when it has rained all day (high humidity?) I will go to start the car and it will start fine, idle at 1,000 RPM like normal starting for a half second, then die. It starts absolutely fine, and I can keep it running with some gas on the pedal, but it just won't idle, that is until it warms up (10-15 minutes of keeping it going with the pedal). Any ideas what can be amiss here?

I called my dealer, and explained the situation in detail, they said that it could be an idle valve, but need to run the diagnostic ($75, 1.5 hours) to check. I bought a Haynes manual, but the only things there are loose vacuum hoses, EGR or PCV problem, clogged air filter, but which one would be related to engine temp and weather conditions?
My car used to do the same thing and a few times died on me unless i gave it gas. I was told by members on here a common problem was the IAC (idle air control) valve are known to go bad on these cars. There are 2 things u can do. U can take it off and try cleaning it with carb cleaner, which works but it more a bandaid. This is what i had done first or u can buy a new one, which is around 40 bucks at the local auto parts place. I have since done that and never had a problem since. First thing i would do is change the air filter if needed, add a new PCV valve and clean the MAF. These all can affect idle esp the MAF sensor and very cheap and or free to do. If this fails I would get a new IAC valve. If that doesnt work then i would get a new Throttle position sensor. These are more of the common not so expensive things i would try first and easy to change. Just my opinion. Also has the fuel filter ever been changed? When i first got my car before the IAC valve acted up my car would have problems starting unless i held the gas and i got the fitler changed and it fixed it.
 

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...sounds like the IAC!

It is about 50 bucks, easy to replace.
If that doesn't solve the problem, well...

Try a new IAC first
 

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engineer76 said:
...sounds like the IAC!

It is about 50 bucks, easy to replace.
If that doesn't solve the problem, well...

Try a new IAC first
Being an engine novice, know a good place online/otherwise to find a drawing or picture of where the IAC is located?
 
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purduechuck said:
Being an engine novice, know a good place online/otherwise to find a drawing or picture of where the IAC is located?

OK if u look at the top of the engine u will see the plenum, the part with the pony on it. On the front of that u will see a cylinder looking thing attached with 2 bolts on the drivers side. There is a little black cap on it too. It has an electrical connection to it and a hose that is connected to it. The hose that is connected to it has a black box in the middle of it. Hopefully someone can give u a pick if this doesnt explain it.
 

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idle problem

I have somewhat of a similar problem with the idle. The engine at times would rev too high at around 2000 rpm even after a 20 minute run on the highway.

Then, yesterday, I was showing my brother in law (auto mechanic) and We troubleshot the problem, I hope...

First We tried checking out the throttle cable to see if there was any resistance..none.
Second, the gas pedal cable, and it also was working fine.

Third, the Idle Air Control Valve and the hose and a little rectangular box connecting to the IAC teed in an L shaped connection....Car was started and was again revving too high (2000 rpm) when the car is in PARK position. He was pinching the hose leading to the rectangular box - IAC and it slowed down the rev to around I guess around 600 rpm. (not sure the exact numbers, instrument panel is analog).

The suspected problem now is the IAC being faulty. Somehow, the IAC valve is not closing as it should when it is supposed to.....Cleaned it out with carb cleaner as others have mentioned in this website and this worked for a few minutes and it was back to the same problem.

Temporary fix (band aid fix), with a tie wrap and a clamp, to minimize air intake and to lower the rev. It worked last night on a 40 minute drive home. Engine revved like a normal engine should at regular and idle mode.

I'm heading to a FORD dealership and hopefully they are open today and have it (IAC) in stock(Sunday, definitely closed on Monday for Labor Day).

I hope the troubleshooting and diagnosis We did was correct or even slight correct.
Please make any corrections if necessary.

Attached is the TEMPORARY FIX to my 00 GT idle problem.
 

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idle problem part 2

:wavey

Forgot to mention, brand new MotorCraft Spark plugs and OEM Ford fuel filter were also installed yesterday prior to the troubleshooting began on the idle problem. :dunce:

Also vacuumed the holes of the spark plugs and the fuel injectors of any debris and cleaned out the fuel injectors spouts(?)

Car was clean, no leaks on the injectors, no misfiring or pinging. So all was good.

Checked under the hood this morning and did a visual inspection for any leak and none were found.

ONE QUESTION : What is that rectangular black box leading up to the IAC, and what does it do? I have the FORD books, (1 thick bible and one skinny one) and tried looking for what that is and unable to find what it is.

Thanks everyone! :laughlitt
 

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gnr_70 said:
:wavey

Forgot to mention, brand new MotorCraft Spark plugs and OEM Ford fuel filter were also installed yesterday prior to the troubleshooting began on the idle problem. :dunce:

Also vacuumed the holes of the spark plugs and the fuel injectors of any debris and cleaned out the fuel injectors spouts(?)

Car was clean, no leaks on the injectors, no misfiring or pinging. So all was good.

Checked under the hood this morning and did a visual inspection for any leak and none were found.

ONE QUESTION : What is that rectangular black box leading up to the IAC, and what does it do? I have the FORD books, (1 thick bible and one skinny one) and tried looking for what that is and unable to find what it is.

Thanks everyone! :laughlitt
I was told it was a silencer of sorts to keep things quiet under the hood.
:winks
 

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Idle problem....FIXED!

Alas! Winchester Autoparts store carried the MotorCraft - IAC valve.

I installed the new IAC, reset the computer, and everything worked great! :kooky:

Ran all the accessories, AC, radio, etc. and took to the highway for a 20 mile drive.
Revved the engine up to 4000 rpm and it did not stick at high rev at all.
RPM slowly went down to normal rev at highway speed.

Revved the engine to 3000 rpm while the car is parked. The idle went down to 750 rpm as soon as I let go of the throttle.

I also wiped on the inside the throttle body where the IAC is bolted on, it was dirty. Guess I need to clean that out next week as my next project.

Thanks to all the info on this website! It kicks ass! :wavey
 

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Discussion Starter #11
How to reset the computer?

gnr_70 said:
Alas! Winchester Autoparts store carried the MotorCraft - IAC valve.

I installed the new IAC, reset the computer, and everything worked great!
I'm going to replace my IAC valve, but how do I go about resetting the computer after I have replaced it?
 
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purduechuck said:
I'm going to replace my IAC valve, but how do I go about resetting the computer after I have replaced it?

Disconnect the negative battery cable for at least 15 minutes. :winks
 

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THanks.

mbhmustang1998 said:
I am glad it worked for ya!!! :happyhapp
Thanks...me too! Very happy to save some dinero working on the car with everyone's point of view in here as well as my brother in law.

I know I'll be here for years to come as I will be keeping my stang no matter how much the gas price goes up! no ricer for me, unless of course I am able to buy it for really cheap hehehehe
 

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Problem Solved

mbhmustang1998 said:
Disconnect the negative battery cable for at least 15 minutes. :winks
Found and IAC valve at Sharp Ford here in Indy - replaced in about 20 minutes (nice location for working - right on top of everything), reset the computer, and after a couple of erratic starts to work the kinks out, it runs fine this morning. Thanks for everyone's advice on resolving my idle issue. This forum was much more helpful than my Haynes Manual.
 
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