high idle - help

[galbre]

Hi,

My 4.6 is sitting at idle in gear at 1200RPM. It has 170k miles currently. This is causing rough downshifts as you come up to a stop sign or light. I have tried several different IACs including one from Ford. I changed the TPS. I have looked for vacuum leaks but I'm unable to find any. Does anyone have any suggestions? I'm afraid this is going to damage the trans eventually as well as just wasting gas.

Thanks,
Gregg

 

[Slade]

I had a high idle issue with my 02 4.0. Check to see if yours has a throttle cable of if it's all by wire. Mine still had a cable that the inner liner had come loose and had bunched up behind the pedal, preventing the pedal from returning to idle position.

I figured it out by getting frustrated one day and putting my toe under the pedal and lifting it. My rpms dropped. So I got under the dash and could see the liner from the cable had come loose and had started bunching up behind the pedal.

http://www.explorerforum.com/forums/showthread.php?t=379141

Here is a post I did earlier this year with images. You can see what I'm talking about with the liner.

 

[galbre]

I wound up replacing the intake manifold and gasket as I had a coolant leak there as well. This seemed to fix the high idle for a while but it is now back. I have cleaned and replaced the IAC and TPS. I also cleaned the MAF and the throttle body as well. I even reset the settings by disconnecting the battery. The high idle is causing rough downshifts as I come up to stop signs and traffic lights.

I also have an issue where the AC is cold but it blows out of the defroster. Could this and the high idle be related due to a vacuum issue? Does anyone have any suggestions?

 

[galbre]

The high idle is also intermittent. I can drive to work and the idle at a traffic light will be 600RPM. I drive home later that day and it might be 1000RPM. What would cause it to be intermittent?

 

[galbre]

I was looking around and noticed that a gray vacuum line was disconnected from the heater bypass valve. The idle so far has slowed down to 600RPM. I'm not declaring success yet until it runs for a few days but could this have been the cause of the intermittent high idle?

 

[Bobmbx]

I was looking around and noticed that a gray vacuum line was disconnected from the heater bypass valve. The idle so far has slowed down to 600RPM. I'm not declaring success yet until it runs for a few days but could this have been the cause of the intermittent high idle?

Yes. And now your ventilation system will probably respond correctly, too.