Here goes nothin. 84 duke 4 speed all stock. Starts up. Runs sort of rough for about 5 seconds. Then smooths out and starts reving up. Stops and idles high untill I turn it off. I have followed ogre's steps on the vacuum lines and we throttle body spray. Even replaced all the rubber lines and the fuel vapor canister. I did notice the cover for the idle set screw was removed so I backed it out a little. Very little difference. I sprayed an entire can of throttle body cleaner all around and it did not stumble at all. I unplugged each he tps while running and no stall. Same with the iac and egr valve. Im at a loss. Any ideas?!

Scan the ECM? Does ECM match the tach? Note that Idle speed w/ scan tool active should be ~1000rpm.

Carefully pinch vac line to brake booster?
Line to booster or booster itself can be a vac leak issue.

Small changes of idle stop then IAC will adjust accordingly.
Too must and ECM can set DTC and/or engine could be hard to start.
reset the stop, See my Cave, Idle Stop

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

I will have to see if I can find a scan tool for that system. I only know how to do the check engine. And I will try the idle set tomorrow.

And 2 things; 1) ogre how did you get so knowledgeable and,
2) I love that quote. One of my favs!

just thought I would post an update. I replaced the TPS and the IAC and even checked the timing, and still had the high idle. today I replaced the temperature sensor for the ECM and when we fired it up, guess what, no high idle! we let the car run for about 20 minutes, and guess what else, no high idle at all and, the cooling fan came on by itself when it reached the right temperature! so if you've tried everything else and still idling high, check that sensor it's the one on the thermostat housing. thanks for all your help and ideas.

Park it in the garage for 6 months. Let battery go dead.

Charge battery, then start.

Damn thing idles perfectly...never did that the 15 years I drove it. Always fast idled at 2500.

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