Missfiring

[Avalon1]

I have a 2001 Avalon and have had some problems develop all of a sudden, it has a miss on acceleration and while in gear at a stop. Had codes pulled the other day and got a code for the maf as well as a po171 code. Went ahead and replaced the MAF along with the PCV and noticed a slight improvement, with the code not coming back, but it still has a miss on acceleration and while in gear at a stop. The last codes pulled after the MAF replacement were P0302, P0303, P0300- Cylinder 2 Cylinder 3 and random missfire, which were not present before. P01135- bank 1 a/f and a P0330- knock sensor bank 2. I have a limited amount of money to spend on the car at the moment and really could use some suggestions. Any assistance is greatly appreciated.

[pmesfun]

When was the last time spark plugs were replaced?

[Avalon1]

Plus were replaced 30,000 miles ago. Pain in the but to get at the back ones. Still trying to figure out why there were no missfire codes before the maf and PCV were replaced.

[eurobob1978]

Did you put iridium plugs in it? I hope so. If not maybe the gap is wrong on the plugs. Iridiums are pre-gapped. Knock sensor usually indicates detonation....maybe bad gas? Put some 92+ octane if you aren't already. Maybe the plug gap got changed when putting the plugs in. I did mine and I hated the rear plugs. not much room to work and I almost smashed the plug just trying to wiggle it in place. You could try moving the coil packs to the other bank to see if the misfire code moves to the other cylinders. Then you would know if a coil pack is bad or going bad. Don't want to guess at those at $80+ each