Re: high idle
 

I set up tps to 0.55v and started the car. after couple of secs idle went down and fell to around 900, I waited adn when the car got hotter I reved it a little couple of times , when it went to closed loop mode idle even got higher adn stayed around 1000, but they are little lower then earlier.

the iac stayed 0, so I think it has a leak somewhere.

I was searching and after engine shutdown I heared some little sucking noise around the back of the engine. I checked hose to fuel pressure regulator and to brake booster , they are ok.

I unplugged the hoose that goes from pcv valves into front part of plenum at the driver side and ended the hose with duct tape to see whats gonna happen. now after starting the engine had around 700 rpm and idled smooth.

so faulty pcv valves? ( I dont know how this pcv ventilation works, just trying to find some diagrams of its connections in the car.)

Re: high idle
 

Ah yes. Sounds like you need the old tie wrap around the upper and lower PCV hoses. I had that same issue when I first got my 92. It was very slight but Mr. Haibeck pointed it out to me.:hello:

Re: high idle
 

How's that? 0 IAC counts means it can't bring the idle down any lower regardless of what tps is. I agree with the others that there is a vacuum leak somewhere (or possibly a miss adjusted base idle screw).
Scott

Re: high idle
 

TPS, at the incorrect voltage will cause a high idle. He has two issues going on, and needed to make the correction of the proper TPS voltage. THe idle did go down, but still not enough.

I agree he does have a vacuum leak, and probably several small ones on the PCV system at either the PCV valves or the Side connection of the plenum for the PCV and Fuel Evap lines.

Re: high idle
 

You should never ever adjust the base screw. That was set by Rochester and never adjusted by MM when the motors were run. Moving this screw just masks the real issue.

Re: high idle
 

I checked pcv rubber hoses, they are ok, everything clamped with steel screw clamps, pcv valves from up side were wrapped around with electric isolation tape because the part which goes to the rubber hose was loose in this hoose. so I changed this tape for new one and make sure it sits tight in this hoose also I put two plastic tie wraps to hold rubber hose+pcv valves+rubber hose in vertical.

that really made a diffrence after starting the car rpms were lower, I drove a mile to my friend and let it idle until fans turn on, it idlet great on low rpms.

while I drove back my foot was little heavier on the accelerator, but reasly road is slippy and I didnt floor it or anything. after stop rpms were annoying high, around 2k slowly falling, I stopped engine, and start it again, rpms falled to 1k.

so any ideas where to look?

one think is the 1k idle and the other is how long it takes for rpm to fall to this 1k level after stop, is it the issue with 1990 chip and only new chip can help?

Re: high idle
 

Jarek,

One thing to try is pulling out IAC and cleaning the pintle and the orifice in the throttle body. They tend to "carbon up" not allowing IAC to close completely even though it says it is commanding 0 steps. Throttle plates may be sticking a bit also. See if you can clean those a bit.

Re: high idle
 

when I took of plenum I also replaced tb gaskets and cleaned iac, but I didnt even look at the orifice in tb, I clean it and iac once again.

btw, I was reading the board and couple of people mantioned a "black goo" in the planum sealing the tb plates. what is it actually and can it be the cause of high idle?

mhm I just thought about something. maybe I`ll start the car with iac out to see if its moved smootly, of course plug the tb hole with something.

Re: high idle
 

Its called dag, and the lack of it can cause a high idle condition. Haibeck has a fix for it if the dag is missing, and you send him your TB. He worked wonders on mine by doing some other "adjusting."

Re: high idle
 

can anyone tell what does he do with the tb ? maybe he puts some sealant there? I`m from europe so sending tb to him would take a lot of time....

I bought a new iac valve, :D, at my friends car parts store, he had it on a shelf, ;) lots of cars uses this iac.

http://img147.imageshack.us/img147/8...1020yk6.th.jpg

I swapped the iac and drove a little. while car is still idles ok sometime 700 sometime around 900-1000, thats not to bad, but when I`m driving it it idles way to high ~1500 rpm, this is really annoying because car doesnt slow down by itself how it should do and for example while reaching lights or some stop and in gear I have to slow it down by breaking more ( the engine pulls a little). its very annoying because even after stop it revs high too long and rpm drop slowly, to slowly to drop to correct rate while stopping or slowing down in normal traffic.

I dont have any fault codes. I`ve been looking for vacuum leak all over. I`ll do it again.... but can it be the 1990 prom issue ? would a custom chip solve the problem? or does anyone have the changes in prom which were made in newer chip for 1990? so I could make those changes on my own by tunerpro or some other software? thanks guys!