Hello!

New member here, hoping that you fine minivan owners can help me figure out my stumbling/backfiring problem before it drives me back to the bottle!

Vehicle:2002 T&C LXi 3.8 155k

Symptoms: backfiring before the cat under moderate acceleration, occasional stumble/miss off the line, at idle, and cruising at freeway speeds. But here's the kicker: its intermittent; it will run perfect with no symptoms whatsoever for a few mins, and then like a switch has been flipped, boom, it runs like *** and sounds like someones making popcorn. NO check engine light, NO pending codes. Had a code for cat below threshold that I kept shutting off, but hasn't come back on since this problem started.

What I've tried: Spark plugs have 1k on them, pulled the front 3 today and they look fine but #6 was a bit grey, plug wires, crank pos sens, cam pos sens.

I feel like the problem has to be electrical because of the ON/OFF nature of the symptoms, which is why I've gone after the sensors. What should my next action be? I'd like to stop throwing parts and money at it until I've pinpointed the problem. Any advice would be greatly appreciated!

 

Had a code for cat below threshold

This maybe loud but take out an o2 sensor b4 the cat then run it if your prob is better or gone U have a clogged up converter.

 

I thought of that, but if it was a clogged cat it would run badly all the time, and my problem is intermitant. It can run like a new van for a mile or 2 and then very suddenly the symptoms come back, and they don't seem to be effected by engine temp or any other variable factor.

 

Not true.....

The "420" code you have been seeing says the cat is leaking internally, so the exhaust gas is going past it with out being measured.

The opposite scenario, is what we are looking for, where the cat material can "Shift" and block the passage.

 

I find that very unlikely because of the frequency of the symptoms coming and going. If there was a chunk of cat on the loose I would think I'd hear it, and if the cat was straight clogged, it would run like *** 100% of the time. I just may try out your theory anyway. whats the best way to get at the up o2 sensor, top or bottom?

I pulled the rear plugs today and they looked perfect, same with the fronts. but then I remembered hearing about dodges being very sensitive to the plugs you put in them; could my cheap autolites have something to do with this even though they have 1k mi and are in good shape? I'm feeling like I should go back to basics before doing anything drastic. I hate this goddamn minivan so much right now it makes me wanna spit!

 

Dont hate on a car because U dont understand how it likes to run.
It only working because of something now working rite figure that out and not guessing and u will be back on the road.