High Idle and fluctuation problem
 

Last night, I took the intake manifold off my 94 because the coolant hoses running to the oil filter burst open and needed to replace those. While I had the manifold off, I gave it a good cleaning with the throttle body off and also cleaned the throttle body. (I took caution as I didn't want to mess up the position sensor.)

Before fixing the coolant lines, my car idled very well around 800rpm (cold start sometimes bogs it down to 400rpm, but once warmed up it is stable at 800)

After putting everything back together, my car will start and stabilize to 800 in 5~10 seconds. but as soon as I drive it or give it a little gas, it idles at 2000rpm for a really long time and then comes down to 1500~1600 rpm. When I step on the brake when its at idle, the rpm starts to fluctuate between 1200rpm and 2000rpm every second. I let go of the brake and it idles at 1900~2000 then if I step on the brake again, the idle rpm starts to dance again. Any ideas on what is possibly broke?
Thank you!

fix your gaskets.


what type of cleaner did you use?

I used sensor safe maf cleaner on the throttle body and superclean on the intake manifold. I bought a new intake manifold gasket when reassembling and I applied very thin layer of silicone gasket on both side of the stock gasket for the throttle body.

Should I take off my tb and scrape off the silicone and try again?

the car idles at proper rpm (850~950rpm ish) if I unplug the ISCV, but if i have it plugged in it idles at 1700 and then after 10~15 seconds it slowly comes back down to 1100rpm...

I guess the valve is malfunctioing?

still idling between 1300~1600, it doesnt fluctuate every second though.

First I tried shorting the ground and ten port on the obd port, and nothing happened, no rpm change and no blinking lights...

I took off the throttle body and the idle speed valve attached to the throttle body and cleaned it with throttle body cleaner.

While the iscv was off, I measured the resistence, my leads were 0.6ohms and the multimeter read 12.4ohms so I guess its in the 12+-1 spec.

When everything was together, I took propane and ran it around all of the vaccum hoses that I can see on the running car, and that did not induce idle change.

What should I do next? I have no clue on what I could do next

Check for a kinked throttle cable or maybe it's not attached properly on the plate?

You can always readjust slack and idle speed.:2cents:

throttle cable is attached properly without any kinks and the plate closes all the way.

I still get random idle fluctuations when i brake to a stop sometimes and sometimes idle comes down to 900rpm...:crx:

check valve in the booster line still good? booster itself good?

Did you ever find what was wrong?

I believe my idle control valve was shot. I just replaced my throttle body assembly with one from ebay and the problem was gone.

I think mines shot too, I'll replace th intake gasket first and see if its fixes the problem. I did everything you did and nothing

You can check if gasket is leaking by spraying intake cleaner around throttle body gasket during idle. if idle fluctuates the gasket is leaking.

Well I've tried all that and nothing...