Within the last couple of weeks, my 2001 Expedition (4.6L) has had some idle issues...
When I am in drive, and come to a stop, like at a red light, the engine seems to surge up and down. This doesn't happen when in park, only when in gear, and is starting to worry me.
What is this a symptom of?
thanks alot

 

Might be IAC. Check out this thread from the Explorer Forum:

https://www.ford-trucks.com/forums/1...pair-help.html

 

Thanks, I will definately check the IAC valve with a multimeter for the proper resistances..

 

Also check out this recent thread:
https://www.ford-trucks.com/forums/5...-ac-is-on.html

I was reading in my Chilton manual last night how the IAC works with the A/C. Sounds more and more like an IAC.
Please let us know if/how you fix this problem.

Thanks!

 

*F65Z9F715HA FTE 65.09

Let me know if you need one.

Ed

 

I am having the same issues with my 98'. Could it be the TPS, I read the voltage and the closed position reads .05 higher than the top end of the range. Any ideas or should I be looking into the IAC also.

Rodney

120K, 5.4L, 3" w/ a 50 series Flowmaster, UNI Filter

 

Hi Rodney,

I happen to have a brand new TPS. I'm gonna throw it on this weekend and I'll let you know what happens.

If that doesn't fix it, I'll replace the IAC.

 

If it's the IAC then you'll experience the symptoms in "park" as well, especially right at start-up...I'm betting on the TPS.

FWIW, mine surged in gear, like you mention, a couple times around 60K miles ago and hasn't done it since.

 

Buzzard, it won't necessarily do it in Park even though it does it in drive if it's the IAC that's going out.

I replaced IAC last night - Problem solved. I still have a brand new TPS if anybody needs one...

 

I have a '99 navigatior that won't idle. The computer gave a code of the mass air flow sensor so i changed that out and it still doesn't idle. where is the iac located on a navigator?

 

Remove the "4.6" or "5.4" cover on your throttle body. On my 4.6, the IAC on the top-right side of the throttle body. I think it's on the opposite side on the 5.4's but don't quote me on that. It looks a lot like this (even though the link is for Explorers):

https://www.ford-trucks.com/article/...r_IAC_Fix.html

 

...Welcome ghman, to Ford Truck Enthusiasts!

See you on the boards. ….