Background:

A few months ago my stroked 92 corvette was having a no-start problem. Every now and then i could get it to start and it would run real rich and want to stall if i was stopped at a redlight and i had it in gear. I could put it in park and the rpms would go normal and it would be fine. No code popped.

I took it to a shop and they checked everything. It turned out that the intake sensor (i'm assuming he ment the IAC) was dirty and he soaked it in some gas (i guess) and cleaned it up. It ran perfect for the last few weeks.

Now:

I was driving in town a few days ago and i popped a code 65. (right side 02) I haven't had time to change it yet. I was driving in town yesterday and as i was stopped at a redlight it started to idle real low again and i had to put it in park so it wouldn't stall out.

The question:

Would a bad 02 sensor cause this or is it my IAC taking a dump? It does run rich. (i can taste the gas when i'm in the car letting it run in the driveway). I don't have any kind of scan tool other than a code reader so i can't read the IAC.

 

When water got into my opti, I never got an opti code but I did get a right bank O2 rich code. It would barely want to run when I had it in drive and pulled up to a red light, but as soon as I put it in park or neutral it would be fine. It's worth a try to at least look into it.

 

The fact that you got DTC 65 doesn't mean its necessarily an O2 sensor problem, or that the O2 sensor needs replacement. Its telling you what you already know... the engine is running too rich on the passenger bank, and the PCM can not correct for that problem using the long term fuel corrections.

If its running that rich, its slowing the engine down at idle, and the IAC "motor" (its not a "sensor", its an actuator) can't provide enough air to bring the idle back to where it belongs. It may be opened as far as it possibly can (counts = 160) or it may not be working. Soaking it in gasoline was a serious mistake. Its got two parts.... a pintle that moves in and out to adjust the idle air flow, and a tiny electrical stepper motor that moves the pintle. You don't want to get the motor soaked with any kind of liquid. Correct way to clean it would be to use a spray cleaner on the pintle only, holding the unit pintle down so the solvent can't get into the stepper motor.

You need to get a scanner on it, and see what is happening. Are the long term fuel corrections bottomed out (= 108) on the right bank? Is the same thing happening on the left bank? Is the PCM responding to the low idle by attempting to move the IAC motor (counts increasing)? Are the counts maxed out at 160?

I suspect these are two separate problems..... rich condition is caused by one thing and is causing the low idle, and the idle problem is caused by the IAC motor's inability to respond correctly.

Have you checked the fuel pressure? Is an injector leaking or sticking? Is the EVAP canister saturated, or the purge solenoid stuck open? Is the EGR valve stuck open? Are you getting intermittent voltages from the TPS and/or MAP sensors?

 

I wish i had a scanner. Every obd1 lt1 scanner i have found have been for 1994 though 1997. I haven't found one that will work on a 92 speed density car.