High idle.

[Dave 88 LSC]

I am trying to solve this high idle I started getting last few days.

Car idles at 1200, and comes down fast from high rpm but gets stuck between 2000-1000, slow to come down to 900. Eventually in drive when standing it will settle to 900 but on the highway I can feel its stuck between 1000-2000 rpms.

I got a code 1506 so I changed the IAC with a new Motorcraft unit.
That didnt help.

If I disconnect the IAC car idles fine at 800 and even drives fine.
New TPS
New IAC
All Ford parts.

Checked for vacuum leaks and non could be found. I wasted the whole can of carb cleaner trying to locate a vacuum leak.

Only thing I can think is, few days ago I changed the passenger side valve cover gasket and we removed the throttle body to do that. Cleaned it up and put it back in. I am thinking perhaps the throttle body gasket didnt want to be reused??? Spraying the carb cleaner around it didnt spike anything up.
I ordered a new gasket, should have it tomorrow.

Am i missing something?

Where is the ground for the CPU?

 

[Dave 88 LSC]

No one has a clue?

 

[NoLimit95]

Read the codes again. All new parts aren't always good out of the box but you swapped out exactly what I would have. I have never reused a TB gasket either.

 

[Dave 88 LSC]

Installed a new TB gasket.
No change.
Are there any vaccum lines behind the motor or intake in Gen 2 cars that I might not be seeing?

 

[stincoln]

iac

I had almost the identical problem and the iac was the culprit...see if you can get one off a car that is known to be working right and give it a try. At least that way you'll know for sure if the new part was good.

 

[Dave 88 LSC]

Can a new Motorcraft unit be defective?

Car idles fine with no IAC. With it it hangs up beween 2500-1000 for a few seconds and slowly settles in at 1000.
Can not find no damn vacuum leaks.

Can a bad EVO actuator be the problem?

I am a bit ashamed... I will have to take the car to the shop on saturday, where good folk there will tell me I need a new quarter panel and a fresh steering wheel to cure this problem.

 

[chris2523]

Can a new Motorcraft unit be defective?

sure why not.
i know people who's job is pull cars that don't start off the line in factories to fix them.
if new parts sometimes don't work for them, sometimes they wont work for you.

 

[Dave 88 LSC]

Solved

I got another TB from a 97 car and everything is back to normal.

Apparently cleaning my TB with carb cleaner has done something to it. I read somewhere that ford doesn't recommend cleaning due to its teflon coating. I dont know how true that is but in my case a new TB solved my problem.