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I have a 1997 4.6 that has just turned a 100.000 miles and it has developed this problem.Not all the time but every once in a while it idles at 1500 RPM.Makes it kind of exciting to drive.I have cleaned the maf and it seemed to be good for a couple of days ,then started fast idle again.No check engine lights lit up.Any ideas would be appreciated.Thanks guys,regards,Jim:(
 

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Discussion Starter #3
I know I am an old fart and just got over finding what a maf sensor was so now I have to find out what an IAC is.If you could tell me I would appreciate it.Thanks,Jim
 

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I actually had my MAF cause a high idle for me. Before it threw any codes it was making the tranny shift weird and sometimes when I stopped it would have a really high idle. Also, when I revved the engine in Park or Neutral it would take forever to come back down! Once I replaced it, everything was perfect. I'm not saying it isn't your IAC because it very well might be, but that's not the only thing that can cause it. Heck even a really messed up TPS could cause it. I've had that happen too.

Oh, BTW IAC = Idle Air Control Valve. It is mounted to the throttle body and is a solenoid that meters the amount of air that bypasses the throttle plate.
 

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Just got to the autopart store and buy the Iac , its the valve that controls the
air intake when at idle . it will cost under 50 dollars .

Youll see it when you pop the hood .And i would also clean your maf wires while
you have your hood open .

Dont forget to reset the computer by either removing the 15 fuse in yor fuse box or disonnecting you bat for atleast 5 minutes .
 

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Sorry! It is on the side of the oh, I see you have a 4.6L. I don't know where it is on there. I would geuss it to be somewhere around the throttle body on the intake and a pipe from it to the exhaust. I hope that helps. Cause I really don't know on 4.6L cars.
 

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bad93bird said:
I would geuss it to be somewhere around the throttle body on the intake and a pipe from it to the exhaust.
Are you talking about the EGR valve? He would be trying to find the IAC, not the EGR valve. IAC doesn't have a pipe to the exhaust. The IAC is behind the throttle body on the 4.6L.
 

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Hello

I have replaced the IAC valve twice and I still have high idle problem, I have to put the car in nutral and floor it so the idle goes back to normal, it's killing me and wasting alot of gas.

Any suggestions ?
 

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I'm thinking that you have other problems causing this. Did you make sure that the numbers on the side of the original one match the new one. I would go have some codes pulled. Now that is the only way to find out what is going on. With your car they can look at it and see what is going on real time. Good luck!
 

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Thanks for all the suggestions guys

I got yet another IAC from autozone and no luck but

I think I have solved it I unpluged my TPS while the engine was on :D and it immidietly started to idle smoother. I gave it some gas and lo a nd behold it whent back down without getting stuck on high idle.

I drove it around with TPS disconnected and it runs fine, no more stickiy high idle.
It actually runs better:eek: without the TPS.

I can hear the wistle sound of the air intake now. and it actually chirped the tires while turning in the parking lot.

I am going to drive for a few days to confirm it works normally then I will replace TPS on weekend and post results.

Thanks for your help fellow tbirders
 

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OK you are welcome. I wouldn't drive it like that for long. Something else may come up and then you will have another problem. Make sure the number on the TPS matches the new one you get. I'd go to the stealership and get it.
 

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master486 said:
Isn't driving with the TPS unplugged triggering your CEL?

The CEL is on caused by the TPS unplugged
So far so good no more sticky idle, tranny down shifts out of OD to soon with out TPS though. Saturday I will replace TPS and see
 

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I finnaly fix it, it was the TPS.
(no TPS =bad gas milage and rough tranny shifting)

To recap: car was gettign stuck on high idle after it warmed up diriving for about 20min.

had to floor gas pedal to get it to idle normaly, this was gettign worse like at every stop light,

Changed the Idle air control valve 3 times:mad:

Dealer gave me the wrong one
Pepboys gave me the wrong one
NAPA tried to sell me the wrong one
(autozone had the right one) I looked at three kinds plastic one is supercoupe, metal with cover to the side is V8, and the metal with top cover is 3.8 NA

The wrong one for the NA 3.8 1990 is a plastic one that the super coupe uses which must be reveresed for it to work.

The correct one is metal just like the original

After changing all those AIC's it never fixed the problem, I disconected the TPS and presto no more sticky idle.

I finnaly put a new one on and it is back to normal.
 

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Discussion Starter #19
Idle problem finally fixed

Just wanted to upgrade you on the fixing of my occasional high idle problem.I almost went out and bought a new I.A.C. valve but upon taking it off I found that loking into the flange area it was very dirty so I got a can of throttle body cleaner and rinsed it out.Put it back together with a new gasket and low and behold the problem still persisted.I talked to a mechanic friend of mine and he suggested that the throttle body could be gummed up.I took the air intake hose off and sprayed the throttle body cleaner in the throat holding the butterfly open.I then wiped it down and repeated till it was completely clean.After all this time this was the cure.I sugest in most cases the replacement of the I.A.C. is not neccessary as cleaning it with trottle body cleaner works great.Regards,Jim:D
 
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