Question'02 Chevy Astro - it does NOT misfire, but I'm getting P0300 DTC. P0300 is calculated based on crank rotation- it's a guess- the computer has no real way of knowning a misfire occured (no exhaust HC being measured, for example.)
Even the GM info says vibration, such as disk rotors or out of balance driveshaft can cause it. And I've read of many stories of P0300 problems caused by many things, such as cam (timing) chain, balance shaft bearings, etc.
Again, my engine runs perfectly at all RPMs and conditions- it never misfires.
Q: do you know of anything that else that can cause it? I always hear a noise just before the MIL comes on- a sort of churning rattle. No noise, no light. Noise, usually light. Engine never misfires. No other problems. Could a bad torque converter, such as stator sprag clutch or converter lockup clutch, cause the P0300?
Thank you!
AnswerHi Rob,
Could be transmission related. A drag from the torque could put enough delay on the crank to appear like a misfire.
How about an accessory? Maybe the drive belt (serpentine) is causing a drag when an accessory starts to lock up. Idler pulley, alternator, etc. Does the sound seem to come from the front of the motor or the rear?
It is one of those things that will become a process of elimination.
Good luck
C J S
