1998 3.0 high idle when clutch is pushed in UPDATE

[dmb2613]

It is worse when it is cold , engine reves to 3000 at stop sign [ manual trans] it will come back down but takes a minute or two. I installed a new IAC valve same thing.
Thoughts please
Thanks David

 

[Uncle Gump]

Vacuum leak...

 

[superj]

Second /\

 

[dirtymike]

smoke test time

 

[dmb2613]

cant find any vacuum leaks, it will come back down to an idle , about 700 rpms when I stop, idles fine until I drive it, does not go to very fast idle [3000 rpms] all the time.

 

[Uncle Gump]

you sure the throttle cable isn't sticky or hanging open?

 

[dmb2613]

today I unplugged the IAC valve and no more fast idle, works fine so there is a problem with the signal coming to the IAC vale , thoughts please

 

[Uncle Gump]

If the truck idles more then about 500 rpm... you have a vacuum leak or maybe someone has adjusted the throttle stop screw?

When the IAC is unplugged... the engine should nearly stall or stall. It would most likely stall if you put it in gear.

Can you read TPS data? At closed throttle TPS voltage should be less then 1 volt.

 

[dmb2613]

idles around 500 rpm

 

[dirtymike]

Still idling around 500?

 

[dmb2613]

Yes, but I hooked it back up this morning

 

[dirtymike]

smoke test time

 

[dmb2613]

I got a Motorcraft one today and all is well. the aftermarket ones dont work for me

 

[dirtymike]

New just means not tested to me. There is a way to set the idle stop screw, tech section.