High Idle?

[mtownfiero]

Is there anything besides a vaccum leak that is known to cause a high idle like around 3k on a 2nd gen 3.1l?

[55trucker]

That ECM you are using is the 3.1 ECM from the Cav isn't it?....so there hasn't been any changes to the program in it?...try starting with the IAC... is the pintle sticking open...or slow in response.. is this a *cold* situation only? Does the idle drop to 1,000 when the engine is hot? Is the throttle plate completely closed? try this also.....close off the throttle body mouth and try to start the engine...

[mtownfiero]

No changes in the program from a cav yet and the IAC is the black sensor at the top of the tb right? I pulled that today from advice off another forum and the the spring with the cone on the end doesnt move when i try pushing it in or anything im not sure if thats supposed to be that way though. My temp sensor isnt registering so i havent let it run more than a minute or so because i dont like not knowing how it its getting but the idle doesnt come down at all. Today i had realized i left one vaccum port unplugged and when i changed that its now down around 1500-2k.

[55trucker]

The IAC should be on the bottom of the throttle body, it is the large horizontal casting bolted the the right side (facing the engine from the drivers side) of the throttle body. Pull it off and see if you can move the pintle assembly by hand (push it in... careful if you try to pull it out, you can pull off the shaft).....there will be some resistance. If you attach the harness after removing the IAC.. turn on the ignition, the pintle should move to the start position, turn off the key and the pintle should extend full so it closes off the idle orifice to stop the engine.

[mtownfiero]

any pics of the IAC?

[55trucker]

Sorry....disregard the prior remark about the throttle body location....have to remember that you;re not using the 2.8 Fiero intake on the 3.1 are you.....

[mtownfiero]

Nope lol thats why i was all confused. Im pretty sure the IAC on a 2nd gen 3.1l is on the top and is what i removed today. The only other sensor on my tb is attached to the shaft that moves the butterfly and would be the TPS. So what i need to find out is how to tell if a 2nd gen IAC is bad or not.

[55trucker]

http://i413.photobucket.com/albums/p...1/P9140038.jpg This is Shawn3091's engine.....you can see the IAC in this picture..as you said, the black molded item bolted to the throttle body.

[mtownfiero]

Ok so since thats it when its pulled is the spring not supposed to compress?

[55trucker]

Well, the spring is supposed to expand...to help close off the IAC pintle when you shut off the ignition. When the engine is running the IAC motor (via the ECM) will retract the pintle shaft opening the idle passage, overcoming the spring force.

[x-thumpr-x]

Does the IAC have alot of black film (dirt) all over it? it might need a cleaning, it could be just stuck in it's place. Did you have to make any adjustments of adapters to hook up the Fiero throttle cable to the 3.1 T/B? It might be that the cable is not allowing the t.b plate to fully close. I had this happen once when my cruise control cable "adpater" pulled apart and would allow the throttle cable to fully retract. It was a slight gab that you couldn't even see with your eyes, but my RPM's would shoot up to 6000. Took some time to figure out why to and in a parking lot 10pm @ night. DOH!

[mtownfiero]

Ok so the spring isnt supposed to move at all when you apply force to it , only when the ecm actuates it. Mine should be working then and my idle is still 1100-600rpms over normal?

[mtownfiero]

The IAC spring a cone looked to have a little surface rust but from the earlier explanaiton it would be stuck closed if anything. I am actually waiting on the throttle cable i need to come so nothing is hooked up the the throttle body that would be keeping it from closing.

[55trucker]

You need to verify that the pintle IS extended to full so that the idle passage is closed. Something you can try is to carefully pull the pintle shaft by hand to extend to full, after doing this have a look into the shaft bore and look to see if the pintle stop is clean & smooth. Also lightly clean off the end of the pintle shaft and now install the IAC back into the bore (do not connect the harness at this time). If it goes back in the way I believe it should the bolts should draw the IAC back in and keep the end of the pintle seated against the stop in the throttle body closing off the passage. Now try to start the engine, if the throttle plate is completely closed the engine will not start (and a code will be set as the IAC is disconnected). If it does try to fire then air is getting in from somewhere else. Troubleshooting is fun, eh?

[mtownfiero]

while removing the iac a bolt broke off in the top part of the tb : (.