I have an 87 305TPI with an automatic bone stock except for the wiring harness that was changed by the previous owner. It idles really high and has since the day i got it. I have checked all the connections and realays and they all check out good. all the sensors seem to be getting the correct volatge. i have tried to set the minimum idle by IAC and it desnt drop below 1500 even with the idle scew COMPLETELY out. the TPS is at .54 at idle and 4.5 at WOT. I have sprayed the intake with water to see if it changes the idle and it doesnt so there is no leak. i have also disconnected EVERY line individually to eliminate that possibility. Could it be my computer? I have checked all the voltage coming from the computer based on the wiring diagram and everything is good. Could the computer itself be fried? The check engine light stays on but it wont let me pull any codes when i jump it. I also tried to run winaldl and it wont give the computer any info. ANY HELP would be greatly appreciated.

the car has the 1227165 ECM in it if that helps.

John34683@yahoo.com

 

I was going to suggest the PCV but if you've capped them then it wouldn't be the problem.
The other thing that would be hard to find is if the throttle body itself has a leak on the top plate or the lower IAC housing.
Take a piece of wood and block off the throttle body and see if it still runs.

 

ok i will try this tomorrow.

 

Can you visually inspect the position of the IAC pindle when engine is fully warm? It should appear seated. Is it stuck open? It can be tested. I believe it should cycle closed-open on cold cold start. that will confirm it can move.

 

I wish you would've given us an update badass, would love to know if and how you fixed it. I'm having the same problem.

 

i replaced the computer and it brought the idle down alot but not perfect. then i checked the codes and it said no codes.

 

Hey man. I am having the same exact problem and was wandering if the new computer is still working good 4 you?

Thanks!

 

So in the beginning the ECM seemed locked up. Now you have a presumed good ECM. Have you tried reseting the IAC since installing the ECM?
My manual (91) says depress the throttle slightly and start the engine at the above idle, running it for 5 seconds and then turn it off while holding it in this position. Leave off for 10 seconds. ALso once you disconnect the battery to clear codes or do service, the ECM takes a bit of time to work the Idle settings back out. Drive it around a bit to make sure it has a chance to re-learn. You my be getting intermittent connections of power or ground to the ECM that causes it to lock up.

 

i had 2 problems with my idle, throttle was hangin up at the gas peddle and the iac was having problems