...for you "EngineCode" experts...

[fasteract]

Wondered if anyone had any thoughts on the source of the following "Engine Code" read out. After a 2.5 hour run, I stopped for a bladder break and returned to find the "CE" light on after the restart. I had been running fairly fast on a 60 degree day, following a Z-06, and had her in "Power" acceleration mode for quite a few seconds fairly often, unusual for my driving style. I also put in 89 grade octane for the first time in years to save a couple cents ! I immediately stopped, shut down the engine, looked over the engine bay (OK, no smells), restarted and had no "CE" on, drove on another 100 miles w/o a problem.

Engine codes were...23,32,34, and 37 (MAF,new 20,000 miles ago), EGR solenoid (where is it?), and both O2 sensors. Last code in series was the EGR. Question...for all I know, can these be old error codes (some of them) since I have had no reason to check for a while, wouldn't the "CE" light have come on before if they were old, can one defect account for all 4 of these codes being present, and which terminal on the diagnotic plug needs to be grounded to clear the memory ?

Thanks for feedback,

Craig

Car is a 1992, just turned 137,000 miles, maintained and faithful thus far.

[Beav]

More than likely the gas had no effect on those codes, especially if it was a one time thing. One or more of the codes could be historical, as you anticipated. When a fault causes the MIL to illuminate and set a code it isn't the result of a one-time situation, the fault had to occur more than once (sometimes several times, depending on the particular fault.) Conversely, some faults will turn off the MIL if they don't recur in, say, fifty drive cycles (depends on OEM, programming, fault type, etc.) Some faults also only turn on the MIL for the moment, and not necessarily set a code. These type faults suck and can be elusive, usually the result of poor grounds or a failing ECM.

My advice would be to clear the codes and watch for any future MIL activity. Check the battery cables and make sure they are clean and tight - just because the car starts doesn't mean they have proper connections.

[CDG]

Hmmm, I too have seen the CheckEngine light come on in the very same way, driving for many miles, pull over, get back in, start car up, and then after about 15 seconds, CE light comes on for about 10-15 seconds, then goes out.
I was told it could be just the ECU making adjustements and letting me know its not teribly happy.
That was about 5000 miles ago, I've had the same problem 2 more times since then. I have not looked at the codes.

My trany was just swapped, so my ECU should be cleared, I'll check the codes when it happens again, perhaps I'll see something??? that I should replace???

[svx_commuter]

I have had the CEL come on a few times too. I check the codes and clear the memory. (don't remember which leads, sorry) If it comes back on again I check the codes agian and see if it's the same ones. If your O2's haven't been replaced in say 100k then they maybe they are on the way out. Someone else says they can be cleaned. A small hole on the outside lets in air and if it get gunked with oil, the O2 doesn't work right. I figured if it lasted 100k miles then a new one should last just as long. I also saved the old ones.

[driverdave]

To clear the memory, insert both leads into the 1 and 2 holes in the diag plug (smaller of the two black plugs), then turn on ignition. That should clear it.

Dave

[CDG]

right, I remember that now, I'll have to do that first, so I can see what my real issue is.
Does the ECU stack all old codes? forever? or just 4 of them?(not sure where I read that)

[svx_commuter]

I think it stacks the codes forever or until they are cleared. I pulled off 8 codes the last time my CEL came on.

[Earthworm]

I also recommend just clearing the codes and seeing which ones come back.

I also recommend having both your battery and alternator checked for optimum performance.

Maybe now would also be a good time to do the alternator mod if it hasn't been done yet on your car.

[CDG]

I have the alternator(wiring) upgrades and it helps in many area's. Highly recommended by many. And cheap.