I recently bought the car off of a guy who said he overfilled the engine with oil and after driving it like that the car started having massive issues. He got it drained to the correct levels, but the issues remained. Idle is high, it's unresponsive and lacks power under acceleration, and sounds like it has a large exhaust leak. The CEL is on and off. During driving it will randomly flash and then stay on constantly most of the time, but it does turn off at times as well. Scanner pulled P-0300 (multiple random misfires). Where should I start in assessing and treating this issue?

 

I would start with your valve cover gaskets to see if it isnt leaking any oil into the spark plugs(spark plug valley). Check your ignition coils and plug wires too. Pull your spark plugs to see if they arent drenched in oil.

I had a similar situation happened to me with my GS300. I changed the valve cover gasket, cleaned out the spark plug valleys out real good and gave her fresh plugs. No more CEL and my misfire wass gone.

GL!

 

That's exactly what I'll be doing tomorrow morning. I'll keep you guys posted on the outcome after that initial assessment, cleaning, and parts replacement (if necessary).