Thanks in advance for any help. I bought a 90 RS. With rebuilt 305 tbi runnin and drives for $250 not to bad. Reasonci got it so cheapxis the guy that had it was tired of messing with it. His son had motor rebuilt and ever since has idled at about 1200rpm I replaced idle air control valve checked timing adjusted idle screw on tbi. No vac leaksxthat I can find what next? Again thanks for any help

 

Is the tps adjustable(slotted), check the voltage. Tbi base gaskets have been known to leak. Check ecm grounds & check the cts resistence at different temps. Try plugging the iac port to see if the idle comes down. Remove the cables at the throttle arm to see if one of the cables is holding it open.

 

Thanks for the reply ex x fire soon as I get home tonight i'll start with those. Maybe the tbi gasket will spray some carb cleaner around and see what happens. Will post with updates

 

since it was a new motor and problem is after that was replaced it could be anything including a vacuum leak you will not be able to find under the intake.

Vacuum leaks are numbe 1 cause of high idle and surging idle. Since you said you adjusted the idle screw I hope you realize that is not an idle adjustment, it is a minimum air adjustment for the throttle body. There is a writeup on this site as to how to adjust it but if your idle is 1200 all the time it won't help. For now I would let the throttle plate close all the way then turn the screw in half turn. You need to leve the throttle blades open a little for fuel to get through.

In the write up I mentioned above it will show you haw to use a paperclip to set the min air setting. During this procedure you unplug the IAC. Leave it unplugged after your done and let the car warm up to full operating temp. If still has high idle looks for leaks now. Pluf off PCV valve to rule it out, plug vacuum to power brake booster to rule it out. Then look for leaks again.

One other thing that causes high idle is a bad CTS. If the Coolant Tempreture Sensor is bad the information the ECM gets is usually -40c causeing the ECM to think it needs high idle and choke. HTH

 

Runnin' like a top tonight. So I changed out the throttle body gasket and and it runs alot better idle in park is about 850 in gear about 750 or just under. Tomorrow. I'm gonna do a tune up to replace the gas fouled spark plugs and should be in good shape. Sure appreciate the help,