2001 Dodge Ram 1500 5.9l 2x2 quad cab....I recently removed my clogged up cat, and have had a rough ride ever since. MPG is horrible...black smoke/**** coming out of muffler, seems to be missing now also. I took it to a muffler shop to be welded, and the guy cut the port to my front sensor off...What do I need to do to repair this? Throughout this nightmare, I have changed wires and plugs, fresh oil change, and have installed one set of non-foulers on the back sensor (non-foulers on front sensor will be done today. The truck is running considerably better, but still does have some problems. Also, what is the Plenum that I keeping seeing threads about. Any advice would be greatly appreciated. And once problems are corrected, should I see an increase in my mpg?

 

Look here for more than you ever wanted to know about your plenum. More than you wanted, but all that you need, that is. You probably need to repair that gasket.

Don't put a non-fouler at the front sensor position. That sensor needs to see the full exhaust stream. The PCM expects the rear sensor to show a cleaner exhaust stream and will set the Check Engine Light if it doesn't -- that's what the non-fouler trick provides.

For the front sensor, you need a bung into which the sensor can be installed. A decent exhaust shop should have them lying around and be able to weld one into place.

Mileage and power will improve when you get a new one in there.

 

you're front O2 sensor is not installed? that's bad.
like hey said, get a bung. drill a hole in the pipe. weld in bung. reinstall O2.

what did the original muffler shop do with your front O2 sensor and wiring. please tell me its not removed, discarded, or damaged. a new O2 would come with a wiring pigtail about 18-24 inches long, and there is an electrical plug in on top of the transmission.

 

If the shop cut the bung out, I would make them replace it.