I have a 2001 Toyota 4Runner V6 2wd with 175,000 miles.

The check engine light came on with error code P0420. I replaced both 02 sensors and then got a cat from AutoZone. The bolts were completely rusted and I couldn't get them to budge. I took it to Midas and they got it replaced for me. They said the AutoZone cat had the flange turned the wrong way so they had to cut it off and insert some extra exhaust pipe to make it fit/connect.

Well, they cleared the check engine codes and as soon as they started the car the check engine light came on. They told me that my post cat 02 sensor was bad.

I took the car to AutoZone and had them check the codes. One was P0304 Cylinder 4 misfire and I can't find the paper with the 2nd code written down but AutoZone said it was the MAF sensor.

Does it seem odd to anyone else that these 2 codes showed up immediately after Midas worked on my car? They were not there before (I checked the codes 1 day before bringing it to Midas).

What would cause the Misfire on cylinder 4? AutoZone said I just need new wires and spark plugs does this sound right?

What about the MAF? Do you think cleaning it would solve the problem or do I need to replace the whole thing?

Any advice is appreciated.

Thanks!
Jeremy

Well, the code for the "MAF" was actually code p1135. The folks at AutoZone told me that the code was for the Mass Air Flow Sensor. Tonight I got home bought a can of MAF Cleaner and soaked the SOB after stripping both screws trying to get them out. I let it dry and put it back in. I cleared the codes and turned on the car.....SUCCESS.....dangit! nevermind....the stupid light came on again.

I checked the code again and it was still p1135. I came home and found this page:
http://www.engine-light-help.com/toy...ine-light.html

Which says it is the O2 sensor after the catalytic converters otherwise known as the Air/Fuel Sensor.

Well, it looks like I gotta take that out and then return it to AutoZone to get a replacement sense it is only a month old.

On another note, the P0304 only comes on during very heavy acceleration. Do you think this would indicate a fuel injector rather than bad wires/plugs???

Any help is appreciated!

Thanks!
Jeremy

And the saga continues...I was looking at the 2nd o2 sensor (i.e. air/fuel meter) and I took a peek at the first o2 sensor........what do you know.....the incompetent morons at Midas who change my catalytic converter never pluged the first o2 sensor back in!!! :behead: What morons!

This is the 2nd time I have had problems with these idiots at Midas and I can guarantee that it is going to be my last! I'm never dealing with those morons again.

Now I still gotta work on the Cylinder 4 misfire. Is there anything they could have screwed up/tampered with/vandalized that would have caused that?

See ya,
Jeremy

Tonight I replaced the spark plugs and spark plug wires on the 4Runner. All in all it was a pretty simple task. I also cleaned the throttle body while I was at it.

After I accomplished those two things, the stutter was gone that I was experiencing at idle and during hard acceleration. My wife also commented that it accelerates much easier and smoother as well.

I cleared the misfire code and after a 10 mile test run things look good so far. Hopefully this will have the problems solved once and for all.

Thanks!
Jeremy