I have a 85 z28 305 tpi. It idles around 1400 rpm when starting and as it gets hot it rises to about 2000 rpm sometimes a little higher. I've replaced the tps, o2 sensor, fpr, coolant temp sensor, spark plug wires, distributor cap, rotor, and ignition coil. I still have the same issue tho, I'm beginning to think something is wrong with the computer

 

Have you tried to do the minimum idle speed adjustment to see if the iac is moving in all the way ?

 

http://www.iroczone.com/2009/10/adju...ir-idle-speed/

 

Looks like there site is down. Follow this procedure.

 

Actually don't think I tried it that way yet. I tried setting minimum Idle but it didn't change anything

 

Did it bring down the idle when commanded in ?
If not the iac might be stuck and needs to be cleaned.
The cts will tell the ecm the target rpm. The cts doesn’t necessarily have to throw a code 15 to be faulty. I assume you have checked for vacuum leaks ?

 

Edited my original post because I haven't tried that yet, I did clean the throttle body a bit when I changed the fpr it wasn't really dirty and changed the coolant temp sensor already. Haven't found any vacuum leaks, egr has been disconnected so I capped those vacuum lines

 

It might be the ecm, you can wrap on the ecms case to see if it drops idle or surges the engine rpm. Here is a link to a 1226870 if you need it.
https://m.ebay.com/itm/1985-TPI-Cama...m_gL4TyW11TQWg

 

Thank you I'll try that and see if it does anything

 

Found out if I turn the key off and on 3 or 4 times before I start it, it will sometimes idle normal

 

Update: just replaced the ecm with a reman one and still having the same high idle issue and fan not kicking on. If i unplug IAC, maf, or tps it still does the same thing

 

Anyone ?

 

- Have you hooked up a fuel pressure gauge and watched it while idling, making sure it hangs out around 30psi when idling?
- Information from the ECM is helpful. Purchase some sort of scanner if you can and post data. A laptop with TunerPro RT and this:
http://www.moates.net/aldu1-and-cabl....html?cPath=64
would be very nice
If you dont want to learn tunerPro you can at least get something like:
https://www.ebay.com/itm/12-Pin-ALDL...r/272388698454
It will dump data to a CSV file as your car is running.
- Youtube is free and just about everyone has the ability to record video, so upload video when you get a chance

 

Haven't checked fuel pressure yet, did fix the fpr tho. Thanks for the advice and yeah I was thinking about just getting a cable so I can see what's going on but I'll check the fuel pressure first

 

I finally fixed the high idle issue I believe. The connector to the coolant temp sensor was somewhat broken and I believe it wasn't making a good connection. When I was testing the sensor today I messed with the connector a couple times and it began to idle down and is now at about 900 rpm