High idle issue, s4.
 

Hello all, I recently purchased an 86 saphire blue FC3S with only 61k miles. Its in great shape but has an issue with the idle. It idles pretty high and i cant figure out why. When I start it up, it usually idles at about 1300 (after the usual 3k, then down to 1.5k cold start stuff) the idle will bounce from 1300 to 1400. Sometimes its slightly higher or lower. The high end being 2k and the low end being 1k. The idle is also pretty rough(sometimes), sounds like it misses every so often and the exhaust smells REALLY rich and gassy. It doesnt seem to be thermowax. It seemed all good when i checked it, throttle cable has plenty of slack, and i didnt find any obvious vacuum leaks. When i tried adjusting the tps, it was way out of spec. I adjusted per aaron cakes ohm method as well as the voltage method, and the screw maxes out before i can get it in a good range. Maxed out, it reads at 1.25 volts. Could that be the only issue? Im not sure where to look next. Ant help would be greatly appreciated. Thanks!

When your adjusting the TPS, is it with a HOT engine (15 min to 1/2 drive) and the check connector jumpered?

If you were to press upwards on the front throttle linkage does this help to lower the idle? The thermovalve cam could be in need of adjustment.

As far as warming up the car, yes i made sure I drove around a while first and it was fully warmed up before trying to adjust the tps. Jumpering the check connector though, i didnt do. Im not sure where that is.
And for throttle linkage, are we talking the linkage thats connected to the tps? Because that one wont move any farther up than it does at idle. Pushing it doesnt yield any results and just hurts my finger.

The check connector is near the lead coil, has two wires, one Orange and one Black.

Progress! I think.... so after readjusting the tps, i can get the car down to a much more reasonable 800-900 range.... until i blip the throttle, then when the revs climb back down, they settle in the 1300-1400 range and the only way i can fix it is by readjusting the tps, which is out of whack again. I readjusted about 5 times and same result every time. Touch the throttle and the tps goes out again. Also the linkage is really floppy where its farthest away from the tps. I dont know if thats part of the issue or if its normal. Thanks all for the help so far. Any more ideas?

The exhaust still smells really gassy and runs a little rougher than i would like. Even with the idle at a much more reasonable level

The TPS voltage reading is based on the position of the piston which protrudes from it. Its position changes w/the rpm going from 850 to 1200 or so, thus you cannot get the same reading under both rpm ranges. Either your throttle cable or throttle linkage is sticking as the likely cause.

Just be silly, on the passenger side theres a richment adjustment (not the proper term) look and see if you can see a flathead screw head. If you can, the factor goop has probably been removed and its been screwed with. You may want to go through the idle reset in the FSM and see what that does

This is a picture of the "richness screw" does it look like its adjusted too rich? Or am i gonna have to dink around with it to find out
https://cimg3.ibsrv.net/gimg/www.rx7...20a5b77922.jpg

It looks normal and that's for fine tuning the air fuel mixture such that it has little affect on changing the idle speed by the amount you need.

I was suggesting it along with the idle screw on top of the TB per the FSM, i was having some wacky idle issues before, and i did the idle relearn according to the FSM, been idleing solid at 750 since 3 years running

Awesome, i will do that after i take apart the TB to see what may or may not be sticking.

i dont know much. but i wouldnt mess around the idle adjust screw.