2007 M45 Misfiring

[M45brasfield]

All,

My 2007 M45 is misfiring at idle and during acceleration. I had the P0300 code, replaced to spark plugs, and it ran fine. the code cleared.

A few days later, the misfire came back without a code. It finally resurfaced a couple days later.

Any ideas on what I should try next?? Someone suggested it could be bad gas or the MAF sensor since its a multiple misfire error.

Any help would be much appreciated!!

[Ilya]

Could be one of those two or a few coil packs. How many miles on the car?

Testing the coil packs is easy. Unplug them one by one (and plug them in before moving to the next) while car is idling. If idle changes = coil pack is good...if idle doesn't change = coil pack is bad.

[EdBwoy]

This is not too common for the V8, but check your intake tube as well. Any loose clamps or cracks in the rubber after the MAF sensor might cause such an issue.
And yeah, mileage would be good to know. Have you ever replaced your PCV valves?
For giggles, unplug your MAF while the car is running to and almost immediately reconnect it. Does anything noteworthy happen?

[M45brasfield]

The car just hit 195K today. Also, I unplugged the MAF while the car was running. The rough idle stopped and on one occasion it seemed like it was going to die but didn't.

Will an unplugged MAF sensor cause the car to die?

[Sstupid]

The car just hit 195K today. Also, I unplugged the MAF while the car was running. The rough idle stopped and on one occasion it seemed like it was going to die but didn't.

Will an unplugged MAF sensor cause the car to die?

It causes the car to go into closed-loop running. It shouldn’t die, just run really rich.