I have an 1997 blazer with 202,000m. When it warms up it starts to misfire and will not accelerate. the more i drive the worse it gets. If i stop for a wile it gets better but then comes back. No check engine light. but if I hook the scanner and clear the computer it starts running good again. I hooked a scanner and read the out put of all the sensors and they look OK. ( all 4 O2= .650ish, MAF=.59, MAP=9.7) today I replace the plenum gaskets, MAP, air filter, pcv and some of the vacuum lines. No difference. I thought I had a bad tank of gas because it when away when i put some Mid grade in but the next tank of Mid grade it came back and wouldn't go away? HELP

 

How long ago was the last tune up? Have you had the ICM and coil tested?

 

Well I cleaned the maf again real good and it seems to have helped a lot, but its still dose it after it gets good and hot. But the strange thing is if i pull over and clear the computer it goes away. I was thinking it was a vacuum leak and the computer is adjusting for it till something goes out of range. Could it be the computer? I put plugs wires cap and rotor 40,000m ago and the might need replacing but it runs so good cool and when I reset the computer.