I have this same code. Just popped up a few days ago. First it was p0305 which was cylinder 5 misfire. So I changed all the spark plugs and felt like it was idling even rougher after the change. So I bought a new coil pack from Auto Zone and replaced cylinder 5's coil. The idle improved somewhat but the engine was still misfiring. So I scanned it again and now I have the vague p0300 (random/multiple misfire) code
. I even hear pops from the exhaust now. When I changed the plugs I noticed that cylinder 3 had thick black grease/gunk around the boot of the coil and the bottom part of the plug (opposite of the tip). And cylinder 5 had carbon dust or some sort of dust and looked really dry compared to the other shiny coil packs. I also noticed that while screwing in cylinder 3's plug, the spark plug socket would stay stuck onto the plug. I had a hard time bringing it back up attached to the extension. So I believe a bunch of grease/gunk was still in there. Additionally, as I was tightening the IM bolts the nut nearest the drivers side just spun infinitely, I must have over torqued it. I don't think there's a leak through there because the other 4 were tightened in the correct order and the EGR is also holding that side down, but I may be very wrong. Don't think its the MAF because I can rev past 3k. Don't think its a HG because I don't have any oil in my coolant, white smoke, or receding coolant levels.
Codes I had before this: P0420 (catalytic malfunction), P1273 (A/F sensor malfunction). And I also have a dead oil pressure switch/sensor, but I doubt its related.
Here's what I have done so far:
- Changed all spark plugs (NGK Iridium)
- Changed coil #5
- New front Cam POS (rear of engine, bank 1)
- Cleaned air filter
- Took out all injectors and replaced o-rings
- Cleaned all connections for coils and injectors.
- Tested front 3 coils, cylinder #5 coil, and front 3 injectors by disconnecting them while engine is running. Those are good.
Game plan from here on:
- Look for intake leaks
- Clean cylinders #3, #5 with a rag wrapped around an extension.
- Drop a Tbsp of ATF into each cylinder
- Check fuel injectors with multimeter
- Move the front coils to the rear since I know they are good. Rear to the
front and test those.
- Replace PCV valve
- Fuel injector cleaner through fuel
- Seafoam through brake booster and fuel
- Replace rear Cam POS (front of engine, bank 2)
- Replace Crank Sensor
- Replace both A/F sensors (its time anyways)
- Get exhaust/catalytics checked for clogs
If none of that solves it then I will have no choice but to take it the dealership and have them scan it with the Consult II and see what they come up with. Hopefully they can tell me what it is and then I'll just replace it myself. Once or If I ever solve it I will come back and post what the solution was. For now the car will stay parked.