I have a 1999 chevy blazer with the 4.3 vortec. I have changed the distributor cap, plugs, plug wires, fuel pump. Cleaned MAF, Throttle body, EGR. My problem is that it starts sputtering during normal driving especially after driving a few miles. It also has some internal backfiring in the engine sometimes when I pull out on the highway. My rpm's fluctuates a couple thousand rpm's from about 2100 to 1900 rpm's at normal driving. Also, the thermostat gauge fluctuates from around 160 to 100 in sequence with my rpm gauge. Im getting very poor gas mileage. Any ideas before dumping a bunch of money in a problem I've seen other people keeping changing everything before realizing all the money they waisted. Any help will be gladly appreciated.

 

Did you have this problem before you changed your cap? If so then I would say probly get your timing checked out. If the problem didn't come till after then it might be a bad cap and arching across terminals, I've had that happen once with a brand new cap on first start up.

 

Well to begin with I changed the dist. cap, plugs, plug wires, cleaned the maf, throttle body, egr over a year and a half ago, because it was skipping. Within the last 6 month it has started the sputtering and backfiring. I will pull out on the road hoping I don't get hit by a transfer truck because it is sputtering like ur on a bucking horse. Then it will surge back and forth at normal driving speeds of 45 to 55. Well after I posted this morning I pulled all my fuses under hood and on the side dash. I found a blown a/c fuse and a cigarette ligter fuse blown. I changed them and drove it around 40 miles with no sputtering or thermostat gauge and rpm jumping up and down as before. I don't think it is fixed, but this is the best it has ran in 6 months and what would these fuses have anything to do with the problem I posted. By the way I just had the fuel pump change 2 weeks ago and it ran well for about one day and started doing the same thing as before with the sputtering and back firing. The fuel pump was bad b/c when u turned the key on you wouldn't here the hum that it makes and would turn over and turnover and not crank until I banged on the fuel tank to get to a mechanic. I don't know what the answer is and don't count on changing a couple of fuses that don't seem to have anything to do with my problem to fix it!!!!!!!! Thanks for any comments on this mystery!!!!!!