01/09/2023
Currently diagnosing a car with an unusual issue. 18 months ago it came in for a P0303, misfire on cylinder three. No big deal. It had over 150K on the odometer so I changed the plugs, they were OE and the bad coil. Out the door. a few months ago it came in for a different cylinder misfire on number 4. Just to be safe I replaced the plugs again and the dead coil. A few weeks later it comes back for the same cylinder misfire. Hmmm, one coil and plugs, normal. 2 different coils and plugs, not unheard of. Same coil again and the plugs are fine, something fishy is going on. I tested the individual cylinder compression and they were great. It does burn oil, a lot, but the plugs are not fouled. Something is making the coils fail and it could be something as simple as a bad ground wire to the ECU. I tested the MAP, MAF, O2 pre and post, crank sensor, cam sensors, fuel pressure, fuel injectors, timing advance, Variable Valve timing percentage, engine load, throttle position signal and about 50 other signals being sent to the ECU. Every signal I saw was within normal parameters. The only code ever in the system is a misfire, P030X. When the coil is replaced it runs fine. I'm stumped. It leads me to the ECU sending a signal to the coils, (3&4) to fire too long or too often and causing them to over heat and fail either temporarily or permanently depending on the amount of heat damage they absorb. Any suggestions?
