tognabologna87

1989 Camaro RS, 5.0l TBI

I've gone through hell and back with this car, and now i'm turning to this website yet again in hopes of a fix.

I've replaced the ICM multiple times, completed a tune up with rotor and cap, placed a holley air breather in place of the stock chunky black one, the coil is an msd coil, the dizzy is (i'm pretty sure) accel or carquest (i work at advance auto parts where i got the car from a coworker) he also removed a BUNCH of emission stuff that i plan to piece back together in the future, so i don't know if one of the missing pieces is causing this problem.

It's had this problem since i got the car. the previous owner had the idle set to 1500, then I took the high idle out. I looked up the stock idle speed and it said the line in between 500 and 1000, in some cases 1000. Ever since I turned down the idle, it does this thing, hot or cold where it wants to idle at 2000 in park/neutral, and 1500 while cruising, then 1200 while sitting at a red light. sometimes it will stop and idle at 750 (where i set it to) for a few minutes and then go right back to high idle again, all on it's own.

i've been told it could be the car putting more fuel than air into the engine, so it's revving higher on its own to have correct air/fuel mixture. so either i have a sensor going bad, or my car is just plain haunted.

any help will be appreciated!

-Tony

stegal

It could be your idle air control. I think that's the name. It is on the passenger side of the carburator. It is a large round part with a big sized nut in it. It is what controls the idle. The wiring to mine was broken and once I fixed that the car idled fine. It used to idle high like your car. If you search on here many have had the same problem. A new one is quite cheap. If your car is running right it should be on high idle for a few minutes and then come down to around 500 rpm. If you pull the part it has a plunger which goes in and out to control the idle. Some times they get gummed up and stop working.

fokeyman

This is the tech for IAC/TPS.

bop11

When he removed that "bunch of emission stuff" what did he do with the vacuum hoses. This sounds like a fuel ratio mixture problem that is caused by a vacuum leak or leaks. Some of the vacuum is controlled by solenoids and that may be why it is different at different times.

ASE doc

AC command will cause the ECM to raise idle, in compensation for the added load of the compressor. If the compressor clutch is disconnected, you will get a big jump in idle.

The quickest way to get a good look at what the ECM is seeing from its sensors and other inputs, as well as what it is doing with this information, is a factory level scan tool. There are several scan tools that have factory level capability on the early GMs. The Snap On scan tools, any of them from the MT2500 up, have this capability. With the scan tool, you can see fuel trims, which will tell you if there is an unmetered air leak, or if the ECM is over fueling. You will also see if the ECM is receiving an AC command from the HVAC controls. The 89 ECM data will show IAC counts indicating how much the IAC is being commanded open.

stegal

Any luck.

tognabologna87

Yeah man, thanks. that's what it summed up to. I don't have a carb, but I still found it all the same. it works currently alot better since I found out I didn't turn the idle ALL the way down, so I did that AND blasted the hell out of the tip of the IAC because it was blacker than the ace of spades. I'm assuming it's sticking or just has worn out. Gas mileage has skyrocketed too. It's still got the random throttle thrusting problem because I haven't changed it yet but that's the first thing being changed this weekend. Thanks so much for your response.

tognabologna87

I'll definitely give this a look into. It's definitely got some fuel issues still, I just wanted the random thrusting to stop. I did notice the high idle would stop upon me switching on the A/C on and off one day, but the next day forward it wouldn't stop idling high until i got in there myself and cleaned the IAC and it's port out, then turned the idle down again because it still was tuned for high idle.

I'm still going to give the scanner a shot though, can't go wrong with that.

tognabologna87

Dude if I had a dime for everything missing under the hood thats supposed to be there, i'd be rich enough to put it all back together. I know for a fact the smog pump is completely disconnected and the only purpose it serves is a belt pulley. The EGR valve is completely gone as well. Every vacuum line i've spotted except for two very distinctive skinny lines leading to where the EGR should be are plugged. I'm looking into making this thing completely stock again, but i have a looooong road ahead of me for that.

tognabologna87

Thanks! i didn't know where to go for something like this but I got my answer anyway, now i know where to point my next idle problem.

fokeyman

No problem. I just got out of my engine. The TPS wasn't giving any signal voltage, new one shows voltage dead on. .55-4.01