Poor Performance

[wlm]

My 1992 Explorer (132,000 miles) is suffering. I've got a slightly rough idle, which really wouldn't bother me if that was the only problem. However, between 35 mph and about 55-60mph, I get a lot of hesitation, chugging and backfiring when the rpm's are between 1500 and 2000 (automatic transmission). If I accelerate quickly, I can "power" through it. My first thought was vacuum leak, but I couldn't find one (although I didn't check with a stethoscope). I've also cleaned the MAF sensor, which didn't really help. Any thoughts? Thanks alot.

 

[EB Bauer]

I would check the timeing and make sure it is fireing when it's suposed to! hope that helps