Help! Got P0420, P0300, P0303, P0304 codes.

[sgt rock]

I have a 02 supercharged 4Runner and needs some serious assistance. It has been getting around 16mpg for awhile now, 122k miles, and is really starting to miss at random rpms (especially when warmed up.) All check engines lights are on so I had the codes pulled and got P0420, P0300, P0304, and P0303. I know what they stand for, but I would like some home help before I take it to a shop.

I checked out the coils and they are good. I was going to replace the fuel filter tomorrow. But what else can I do? I live in Nebraska and all we have here is 89 octane with Ethanol added. Sorry for the random information.

Thanks!

 

[Nelsonmd]

I have a 02 supercharged 4Runner and needs some serious assistance. It has been getting around 16mpg for awhile now, 122k miles, and is really starting to miss at random rpms (especially when warmed up.) All check engines lights are on so I had the codes pulled and got P0420, P0300, P0304, and P0303. I know what they stand for, but I would like some home help before I take it to a shop.

I checked out the coils and they are good. I was going to replace the fuel filter tomorrow. But what else can I do? I live in Nebraska and all we have here is 89 octane with Ethanol added. Sorry for the random information.

Thanks!

Have you checked the spark plugs? There have been a good number of threads about misfires here, so searching more should net you some other things to check.