87 305 TPI, 5 speed. The idle is high it gets higher as the car warms up. The TPS is set at .54 closed as it should. THis problem is persistant and never fails. A cold start idles at 900 on the tach and as it warms up the idle gets to 1500. The idle stays that high until it cools off again. I was thinking maybe the computer is getting bad engine temp info. Any input helps thanks.

 

Also with the TB coolant bypass done, no coolant flows thru the TB where the sensor is, so does the same sensor pick up the temp properly?

 

The coolant temp sensor isn't in the TB.

Are you sure the idle speed is REALLY changing; or is it just perhaps, your "tach" (wavy-pointer "sporty" trim package in the dash) is fornicated, and lying to you?

 

scan for codes first, i would be thinking along the lines of a vacuum leak or issue with your IAC idle air control valve

 

Thanks.
Yes, it does actually idle high, not a tach issue. I can start it and let it sit and warm up without driving it and the rpm slowly rises.
It doesn't set off a code.


Sorry I mean this one in the intake below the TB.
http://ww2.justanswer.com/uploads/am...1_235448_1.gif But temp cant make the computer affect revs?


I have used propane and carb cleaner to try and find vacuum leaks and haven't found any. But I was also unsure why a vacuum leak would only start after the car warms up.


If the IAC is to blame, would it make sense that the idle is higher when warm?

 

Check your "minimum air" setting. Search this site for that phrase.

Probably wouldn't hurt to disassemble and clean up the IAC... they get pretty gunkified sometimes. Again, do a search, find somebody's post that knows what they're doing (Vader for example), it'll tell you everything you need to know.

 

I was thinking IAC, too...what are the counts at idle, and are they increasing as the idle increases? IIRC, they should be somewhere around 20 normally on a warm day.


If the counts are staying steady, but the idle is actually rising, I'd suspect a vacuum leak that gets worse when the engine temps rise.

 

Are these the full steps for the minimum air?




"To adjust the minimum air, you must first install a jumperon terminals "A" and "B" on the ALDL. Do this with the keyon, engine off. Wait about 30 seconds or so. This will allow the IAC motor tofully extend and close off the air bypass. Without turning off the key, pullthe connector off the IAC motor. Start the engine, and let it warm up fullybefore adjusting. Then it will be at the minimum speed set up. Set theappropriate idle speed specified for your application found in your automotivemanual, typically around 450 rpm for the TPI cars. Use the correcttorx bit end tool to move he idle screw in or out to achieve the proper minimumair speed. Now you can set the tps to the correctvoltage."

 

Well during some simple diagnosis I discovered the timing mark on my harmonic balancer isn't "where I left it" when timing was done over a year ago. In fact the timing mark is no where in sight with the timing light. The distributor is still tight. I might be replacing a balancer as my first duty.