can a post flow o2 sensor cause multiple misfires under any circumstances? i finaly realized today that the o2 sensor is bad so ill be replacing that soon. i had it scanned and it shows multiple misfire. just wondering if the o2 sensor could cause it.

 

No, but this can.... https://dodgeforum.com/forum/2nd-gen...um-thread.html

 

yea i know that thing i got one comin soon

 

Then you already know a clogged cat is most likely what's causing the misfires I guess.

 

i was thinking that could be the problem but the cat is not even a year old. plus it was doing the same thing before we replaced it. when we changed it out it made no difference.

 

The cat went bad because of the plenum. You need to fix that problem. Then you can diagnose other issue's. Fix plenum, replace cat and pre cat o2, do a tune up. Depending on how bad the plenum is, it can take a lot less than a year to ruin it.

 

ill be doin that sometime this week. would it be best to replace the cat after i replace the plenum regardless of whether its bad or not?

 

It's best to replace or gut it at the same time you do the other work. Why fix one thing and not the other? Besides, a clogged cat can lead to cracked heads.

 

how about cheater pipes with o2 ports? completely remove the cat from the picture.

 

If you can get away with that where you live, go for it. Check the DIY/FAQ section for the non-fouler trick, to prevent the PCM whining about catalyst efficiency.

zman has it nailed though. Do the tune up when you do the plenum. It just doesn't get any easier as when the intake is out of the way.