Misfire problem

[billh]

I have a friend with a '92 MTX car, 90,000 Miles. Car has been properly maintained. The car has a misfire under load problem. If you accelerate in 4th or 5th gear under load, say from 55 MPH, it acts like the timing isn't advancing. The engine will misfire. If you down shift to 3rd and run it in the upper RPM ranges, it seems fine. Has a slight stumble in lower gears. All to the usual suspects have been tortured properly to no avail. Plugs and wires replaced, no oil in the wells. It set a cam position sensor code, replaced but problem still not solved. The tech says there isn't as much diagnostic info available for the '92 as for later cars.
Weak coil pack? The MAF was cleaned not too long ago.
Ideas, anyone, Scott?
Thanks

 

[96lt1]

im not an expert but i was having similar problems and it was my throttle position sensor. autozone can test them and they are only like 20 bucks. i dunno for sure if that would be it but its worth a shot.

 

[sdpatt]

Misfire + no codes = plugs + wires.

 

[billh]

sdpatt:
Misfire + no codes = plugs + wires.

Thanks Scott.
That was my thought. They tell young doctors that when you hear hoofbeats, think horses, not zebras.