Wondering if the beast is missing a temp sensor input, believes itself cold.

After a 10 minute drive I'm still idling around 1800rpm. Sometimes a "kick down" like the old carb days, will bring the idle back to around 1000.

Curious if this is another 4.0L failure mode.... most likely suspect? TB was cleaned several years ago, but has never been removed AFAIK.

Thanks folks.

 

Look for a vacuum leak first.

Run a self test on the EEC to see if it's captured any error codes.

 

make sure the air tube from the air filter box to the intake is not torn or leaking at either end. Remove it and inspect it for tears.

If torn, repair with a flexible gasket maker.

 

Believe it or not, I've never pulled codes from this Van in 24 years! Found the EEC plug, Youtubed the jumper pin position, warmed it up completely and.....

No codes. Neither KOEO nor KOER produced so much as a BLINK in my system display! My Aero has the digital dash, so the bottom line of this LH display area is the CHECK ENGINE. I can't even get it to blink a 3 count for 6 cylinders..... as the Youtube videos show. Zip, zero, zilch, nada.

Finding a vacuum leak is going to be a joy, if that's all that is left.

 

Don't forget the IAC mounted on the side of the throttle body. They gum up from dirt and EGR junke, also mechanical wear item.

Unplug the wires to the IAC, check for idle change. Ran by PCM with a PWM high speed data signal

Some have luck cleaning, most don't

 

Yes sir, I knew the IAC was a suspect, wherever it was! I'll test it... no doubt, an IAC stuck open (or randomly open) would cause the high idle. I'll report back my findings.... thanks or the tip.