My "D" is an 02, stock, no mods at all, 220k on it.
The exhaust was smelling really bad and mileage decreased a lot.
I was getting several varying error codes. I found some corroded connections at the map sensor connector, cleaned that and the mileage returned - exhaust smells ok now.

But I am still getting an error code P0402. When I clear it it will run a day or two OK and then in the morning, when cool, it will trip. I thought at first it might be the gas, so I ran some cleaner thru the tank, changed gas companies and three tanks later I see no change.

So is it more likely to have a bad rear 02 sensor or is catalytic converter bad?

And as I am messing with the exhaust I have never been happy with the sound. It is to quiet. I am not wanting LOUD. I would just like a lite rumble at idle and a bit of noise under acceleration.

Any suggestions?

 

Has no one any suggestions?

 

It could definitely be an O2 sensor is causing bad mileage. I had a bad O2 sensor in a car and mileage dropped by over 1/3. Is it running rough? If it was running rough it could also be a timing issue caused by the crank or cam sensor. As for exhaust look around on youtube and you can find videos of different exhausts on your motor to get an Idea what they sound like.

 

You say it smells bad, what does it smell like? usually converters smell like rotting eggs when they go bad. The rear o2 sensors only "job" on our trucks is to tell the PCM if the converter is doing its job. The front o2 sensor is the one that controls the fuel mixture and its possible that its bad and sending the wrong signal to the PCM causing it to run to rich or lean in turn leaving you with the worse gas mileage. That could also be the cause of the "bad" smell too..

 

Swap out the cat AND both O2 sensors. All are very old anyway.

 

This...and get yourself a way cool cat back exhaust system.

 

Oh, you mean like this one I put in a few months ago? Magnaflow, baby!

 

Confucius say.......man who have sex with tail pipe get hot rod.

SJ02

 

 

Yessssss. Magnaflow here too. One in two out the sides behind the wheels....love it

I have the less shiny version though.....us poor techs ya know.