Code P0300, multiple misfires

CAPERDUE

MEMBER
2003 CHEVROLET MALIBU
3.1L
6 CYL
2WD
AUTOMATIC
160,000 MILES

The car was misfiring a little, every once in a while. But was running overall smoothly. So I replaced the spark plugs and wires. Now the car is misfiring pretty bad at idle and throwing code p0300. Double checked to make sure I had the firing order right and it was fine. And I'm getting fire to all cylinders, but when I pull the wire to check for spark it arcs up to 2 inches away. Do not know if that's normal. Checked for vacuum leaks but found none. Wondering what to do from here.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Welcome to 2CarPros.

The spark you mentioned is excellent. If it jumps that far, you have a good coil. Now, many things can cause a random misfire. Is that the only code you get? Have you checked things such as fuel pressure? You mentioned checking for vacuum leaks. How was that done? Even a bad crankshaft position sensor or dirty fuel injectors can cause a misfire.

Let me know if there are other codes. Also, here are a couple link to help with checking fuel pressure and injectors:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Also, if you have a live data scanner, let me know what the fuel trims are and what the engine coolant temperature sensor indicated.

Joe