DO ECM LOOSE CALIBRATION OR RESET REV LIMIT PARAMATORS?
2003 CHEVY MONTE-CARLO SS 3.8 V6 ENG CODE K. CAR STUMBLES AND MISFIRES AT 4,000 RPM UNDER HEAVY ACCELERATION. ONCE PAST 4 GRAND ENG SEEMS TO RUN FINE. ENG RUNS FINE UNDER ACCELERATED LOAD UP 4 GRAND AS WELL
You said it runs fine past 4,000 rpms...at what point past? Like, does it break up in a specific rpm range, say 4000-4500 and clear up after that? To answer your question...No, the rev limiter is a function hard-programmed into the engine computer and will not lose memory. What *can* lose memory is fuel trim tables primarily, along with IAC position and some other things aside from the more obvious interior items like radio, power accessories.... The fuel trims will take a little bit of driving to get back to normal and some vehicles are more sensitive to losing these tables than others. Any Check Engine lights or stored codes?
ENG SEEMS TO RESPOND NOMINALY AFTER IT PASSES 4500 RPM. WHEN THE ENG WAS MISFIREING BADLY THE "CHECK ENG LIGHT" JUST FLASHED REPEATEDLY BUT RARELY SET STEADY ON. WHEN I DID GET THE SES LIGHT TO SET ALL THE CODE WAS P0300 "MULTIPLE MISFIRES" LATELY I HAVE RUN A TANK AND 1/2 OF 93 OCT GAS AND ADDED BOTTLES OF "HEAT" TO THE FUEL THINKING I HAVE PICKED UP SOME WATER OR BAG GAS
RPM specific, especially with that tight of a window, is pretty odd.... See if you can find someone that will datalog it for you. But as of right now, with you symptoms, I'm leaning towards possibly a faulty mass air meter, though this is a bit strange even for that. Try unplugging the meter. I know it will throw a code, but it will make the car go into a "limp mode" and it will run off of pre-calibrated fueling tables. It will be rich and be down on power, but if the MAF is the culprit, your miss from 4k to 4.5k will disappear. Update us after you try. If this doesn't work, plug it back in and have Autozone or someone clear the code for you so if you're able to get it datalogged, the technician isn't chasing a bogus code. And obviously always plug and unplug it with the engine off and key out.
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