I have a '93 K-1500 4.3 no air pump new engine all new pollution components the thing ran great for three years with glass pack muffler put on regular muffler now runs like crap. Unplugged o2 sensor and it runs good. Please advise if possible.AT 4WD

 

Dump the glass pack. They are crap.

 

I did, put regular muffler on then it started running like crap. Unplugged O2 sensor it runs good replaced O2 sensor runs like crap.

 

Run a scan-tool on it and see if any codes.

 

Clogged catalytic converter

 

No codes no catalytic converter

 

muffler on backwards? Some are directional.

 

Little Bear you were right. But get this, muffler was wrongly marked! Never seen that before! I worked at a muffler shop and installed 100s of exhaust systems never once seen a muffler marked backwards. First time for everything I guess. Thank you for your response. I don,t think I would have even tried turning it around. Threw the thing in the scrap pile. Back to the Thrush glass pack again, runs great. Spent a lot of time on this truck need to keep it on the road just to justify the time and money ha ha. Wife calls it the money pit.

 

More defective brand-new parts. Seems to have become the norm these days. Muffler either made in Asia/Mexico, or perhaps in the USA by a PO'ed minimum wage worker who didn't care.

 

Good deal, always good to get feedback, glad I was able to hit this nail on the head for you!