This is my vehicle 1994 Eddie Bauer Explorer 120,000 miles
recent tune up (3 months), oil change (last week), new muffler (Flowmaster) (2 weeks)


Original problem: Loss of power/acceleration while driving. Thought it was the Catalytic Converter (got a quote for $750 to replace entire exhaust), second opinion said that cat was fine just need new muffler.

Current problem: Rough idle after reaching operating temperature. Feels like it is gonna stall out around 600 rpms. There is also a strong exhaust smell (skunk, rotten egg, etc).

Replaced: EGR Valve (fixed loss off power problem), EGR Sensor, cleaned MAF.

Current code reading: Mass Air Flow Sensor below minimum voltage (157); Heated Oxygen Sensor indicates lean condition, left side (176); Heated Oxygen Sensor indicates rich condition, left side (177).

The MAF problem didn't appear until after I cleaned it, I hope I didn't damage it. (But I didn't reset the memory after the cleaning.)

Is the O2 sensor bad and if so which one? Would a bad O2 sensor cause the smell and rough idle? Since I am not getting codes for TPS and IAC I am thinking they are still fine.

Thanks for the information.

Found a lot of useful stuff thus far.

Jac187