1999 Explorer cold start idle

[rp23g7]

My 99 4.0 explorer wont idle during cold start, i believe the air charge sensor may be bas.

Where is this located? The Repair book shows it on the upper manifold somewhere, but i cant see/find it.

Can anyone give me a idea where it may be, or am i looking straight at it and not realizing it?

 

[James909]

The air charge temp sensor is integrated into the MAF sensor on your '99. The earlier years had a separate sensor mounted on the upper intake like your repair book indicates.

 

[rp23g7]

Thanks, so should i just buy a MAF for it?

 

[James909]

No, I'm not convinced that the air charge temp sensor is causing the problem. Does it idle OK when the engine's warm? SOHC or OHV engine?

 

[rp23g7]

Thanks for repying James

Its the SOHC motor, Yes it idles fine when warm or if the ambient temp is over 70-80 degrees cold start.

Idles like garbage untill warm in the mornings, but will idle fine if its been sitting out in the hot weather after a 8 hr workday. (I.E Summer time) Yes, i am a procratinator.

 

[James909]

Is the CEL on? I have a feeling that the intake manifold O-rings are leaking. It's a common issue, there was a TSB on it. When it's cold out the O-rings shrink and you get a vacuum leak, hence the bad idle. When the ambient temp or the engine temp is warm the O-rings expand enough to seal the leak.

 

[rp23g7]

Yes, the Check Engine Light is on. I can reset the computer and it will stay off for a few days.
Speaking of O ring leaking. I can smell a oil leak that has developed recently. The bad idle has been around for a longer time.

Havent searched for it yet but the oil leak seems to be hitting the exahust manifold as you can smell it after the engine had been running.

Would the O-ring leak oil or just engine vacume?

 

[James909]

The intake O-rings wouldn't leak oil, just vacuum, so the oil leak is unrelated. You should get the codes read, if they're lean codes then my money is definitely on the intake O-rings.

 

[rp23g7]

Thanks James I will have it checked out. It doesnt look like its too hard of a job to replace the gaskets.

 

[martin ashton]

99 explorer 4.0lt cold start idle problem,O rings ?

Can anyone help with this problem, what sort of a job is it to replace the O rings, will i need any special tools and are the parts easy to get.By the way I live in rural SW France but have a very good friend who lives in Oregon .Many thanks in advance.

 

[James909]

How-to thread

 

[ckelly444]

Is the CEL on? I have a feeling that the intake manifold O-rings are leaking. It's a common issue, there was a TSB on it. When it's cold out the O-rings shrink and you get a vacuum leak, hence the bad idle. When the ambient temp or the engine temp is warm the O-rings expand enough to seal the leak.

 

[ckelly444]

Intake O ring Leakage

Ditto me with the o-ring leak. Been there done that. Runs fine in 40f and above temps. L/M dealership picked up the tab on repair even thought vehicle was way out of warrany. Check it out. Next guess would be IAC valve is dirty. Takes about 15 minutes to remove, clean and replace, Good luck!