Replaced Catalytic Converter and Fuel Economy Dropped

1992Jimmy

I went to a transmission shop because my Jimmy was having trouble accelerating on an incline. Also, my coworkers commented on a rattle coming from the Jimmy. After a drive, the transmission tech said the transmission was fine, but the poor acceleration and rattle indicated the catalytic converter. An exhaust shop replaced the catalytic converter with a "universal" model. The acceleration problem and rattle are gone, but I'm losing about 70 miles per 3/4 tank. Any suggestions before I go back to the exhaust shop? Would an OEM part (if I can find one) be better?

Mr_Shiftright

How many tankfuls did you run to check the MPG? Did the shop replace or mess with the 02 sensor? Maybe the truck needs to be scanned to check air/fuel mixture and behavior of the 02 sensor or sensors. This is an old truck so there could lots of things in play here.

1992Jimmy

I normally refill at 1/4 tank once a week. After replacing the converter, I noticed I was refilling once every 5 days. The O2 sensor wasn't replaced. I replaced the MAP sensor in April. I'll have the air/fuel mixture checked. Thanks.