ok im a chevy guy and just traded mine for a 1996 dodge 2500 4x4 with the 5.9 gasser. it has 160,000 on it. i just did and oil change new air filter and new plugs. i took it to a exhaust shop and got true duals but the guy who had it before me gutted the cat and hacked it all up beyond repair. so they cut it out. now both my sensors are hanging. can those be open or do they have to be in the pipe?

Also want to know what other "needs" to be done for maximum performance.

 

you need the o2 sensors, at least the front one. The exhaust shop, if they were any sort of decent shop, should be able to weld a bung into your pipe for the o2 sensor. As far as everything else i would start with checking the Plenum which you can find a thread all about in the DIY section.

 

ok so the upstream has to go in? and just reminding there is no cat. just duals.

 

Plenum thread is stickied at the top of this forum. Everything else is in the FAQ/DIY section.

O2 sensors MUST be in the exhaust stream. Put a couple non-foulers on the rear O2. (that trick is in the DIY section.)

 

the best compromise is to put the front o2 back in the passenger side pipe so it can provide fuel trim feedback to the pcm. then, as a first step, leave the rear o2 out and tie it up out of harm's way. if you get a CEL about rear o2 cat efficiency, then you'll to put it in the pipe, maybe with a non-fouler spacer.

without the front o2, you run a risk of an eternal CEL, and rich mix, and poor mpg.

 

i thought so i drove it alittle ways after the exhaust was done. it just seems like it was CHUGGIN fuel so i figured id ask. also i looked over the motor and looks to be a newer water pump. one less thing i gotta do

 

Check the plenum..........symptom is chugging gas qand oil. And my guess is that is why the cat was gutted!

 

You remember that dude here, I can't remember who it was, that claimed to get a mpg or two better with the downstream O2 OUT of the pipe?

 

I remember that. I also recently did considerable work on my Yota, including changing a cat with 275,000 miles, both O2 sensors, and other things to get mileage increase. Got it up from 16 to 19.58 with 2 months of testing over 4000 miles. Then tried it with rear O2 out and port plugged. Absiolutely no difference...except seting code.... Tried that for about 800 miles (2 trips to Austin and back). I thought about calling BS on that after my experiment......

 

Interesting results.. I wouldn't doubt if it was BS either....