Engine idle speed

[Tanners]

I am working on my daughters 98 explorer with the 4.0 sohc engine and 24700 miles,sometimes the rpm will drop to around 400 rpm them back up to 550rpm. It will do this 3 times then die if you dont give it the gas. I am thinking its the TPS but my question is what is the normal rpm in gear. Thanks for any advice.

 

[SoNic67]

IAC valve is worn out. Replace it, don't bother to clean it, there is nothing to be cleaned inside.

 

[koda2000]

one of my V8's idles a little high for my taste (around 1000 when warm). IAC? TPS? it idles very steadily, just too high compaired to my other two V8's.

 

[Tanners]

I replaced the IAC 2 months ago, at that time it would not idle at all when cold.

 

[mcfoss1]

Check MAF and IAC. To check IAC let the engine idle and unplug it while its idling. it should completely die. If no change at all then it is prob bad. Also since you just replaced it take some starter fluid and spray around the iac to make sure it got a good seal and is not sucking in any air. Do the same all around the motor to check for vacuum leaks it may have a leak somewhere. Is there any codes? Also have you checked the fuel pressure?

 

[SoNic67]

IAC valves from parts store, OE from dealer or junk yard are very different animals.