Im new on here, so please forgive me for this being my 2nd post. But Ive been having a check engine light on for a long time and I cant seem to get rid of it. Im a mechanic (backyard) and I can work on it, but cant figure it out. Im getting a lot of codes. one is P0300 (multi misfire) along with cylinder 1,3,4,5 misfire codes. Weird! and the main one that has been there a long time is P0420. Ive done some things already, new EGR, new sensor, and cleaned the top intake manilfold out. Please help me! Thanks!

Bryan

For cylinder misfires: http://www.odyclub.com/forums/showthread.php?s=&threadid=32106&highlight=P0300

For P0420 Cat Coverter:
http://www.odyclub.com/forums/showthread.php?s=&threadid=54096&highlight=P0420
http://www.odyclub.com/forums/showthread.php?s=&threadid=21162&highlight=P0420

Im new on here, so please forgive me for this being my 2nd post. But Ive been having a check engine light on for a long time and I cant seem to get rid of it. Im a mechanic (backyard) and I can work on it, but cant figure it out. Im getting a lot of codes. one is P0300 (multi misfire) along with cylinder 1,3,4,5 misfire codes. Weird! and the main one that has been there a long time is P0420. Ive done some things already, new EGR, new sensor, and cleaned the top intake manilfold out. Please help me! Thanks!

Bryan

Check your gas cap, usually a loose gas cap causes the "check engine" light to come on so make sure when you tighten it you hear about "5 clicks".
Goodluck.

I am sorry but the gas cap issues does NOT cause P0420 and the cylinder misfire codes. The gas cap issue has its own code.

But it wouldn't hurt to check the cap any way.

:)

Thank Ya'll very much. I hate a check engine light, hopefully I can get to it this weekend.

OK the light still comes on. The misfire code went away, not sure why that code came on. Been only about 1.5 years since I did a tune up. I did the defouler thing with the O2. Came back on after 280 miles. I have a new EGR and cleaned that port. Do I need to take the whole intake off and clean it? I also I have a new Cat as well and the O2's are only about 2 years ols and have about 25k miles at the most on them. Thanks for any help

Bryan

OK the light still comes on. The misfire code went away, not sure why that code came on. Been only about 1.5 years since I did a tune up. I did the defouler thing with the O2. Came back on after 280 miles. I have a new EGR and cleaned that port. Do I need to take the whole intake off and clean it? I also I have a new Cat as well and the O2's are only about 2 years ols and have about 25k miles at the most on them. Thanks for any help

Bryan

I've read maybe once or twice that sometimes a replacement 02 sensor can go bad...might be worth checking them.

btw, are all the codes back? or is it just one?

I've read maybe once or twice that sometimes a replacement 02 sensor can go bad...might be worth checking them.

btw, are all the codes back? or is it just one?

Ok, I'll check them. Only one code came back and that was the P0420 code.

I had the same problem with my 98' Explorer. I had that code for years, with no real decrease in performance. But last fall it started running really poorly. The fix to the problem was replacing the Cat(s). I know there is a lot of debate over replacing O2 sensors in fixing this problem. But from my own experience, changing O2s didn't really do anything. I just got my Odyssey and the poor Explorer doesn't get driven anymore! I hope you figure it out.

I finally figured it out. Well at least over 200 miles now. The thing I did to fix it was change my Valve cover gaskets and spark plug gaskets. The plugs wew soaked in oil and cause a multiple miss fire and the P0420 code. With new gaskets and plugs, its running good and no check engine light!

Glad you figured it out, good job!