vehicle: 2000 jimmy 4x4.

problem: under load when cold,( lessens up when warm but still happens more frequently), engine bogs under acceleration past half throttle. if i baby it, all is well, revs up good with no load. has new tune up , airfilter, oil change, fuel pump, and fuel filter and lines. has no codes, no check engine light, no history codes either. any ideas? watched live data on scanner. o2s 1 and 2 bounce between rich and lean at idle then stay lean when accelerating. not quite sure what this means but it also seemed to show misses on cyl# 6.

 

Have you cleaned the MAF sensor?

 

Sounds like it could be your cat on it's way out.

 

No, i havn,t cleaned the MAF. Do you have a voltage reading on what it should be around?. Whats the best for cleaning it? ive used CRC's MAF cleaner before and i really didnt see any change, on a difernt vehicle. How would i check to see if the cat. is going bad?

 

MAF sensor output is a frequency that corresponds to the airflow going into the engine. You really cannot test it without some more specialized tools/equipment. Check out the Tech Article (DIY) section for a how-to.

As far as the cat goes, you could remove one of the pre-cat o2 sensors and drive it. If it accelerates better, your cat is restricting flow.