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2002 4.3 blazer misfireing at level speed only( PO 128 Code)

02-16-2009, 05:55 PM
My 2002 4.3 Blazer Will misfire when While running at a level speed, but when I get on it, it runs fine. It's worse when you add any kind of moisture (rain,snow,high humid, ECT). I've change plus, plugwires, airfilter and startd to run Techron through the tank. It's throwing a PO 128 and knowone seems to know what that code stands for. Please any help would be greatly appreciated!!!!

02-16-2009, 06:01 PM
P0128 is indicating that the coolant temperature is too low. Most likely replacing the thermostat will take care of that.

What brand of plugs and wires did you use? Did you replace the distributor cap and rotor? Plugs, cap & rotor should be AC Delco ONLY.

02-16-2009, 06:11 PM
Yes, I replaced the plugs Dist cap and rotor all with AC Delco parts. I resently gutted my Cat because it was melted shut. So I assume thats why it's running cool.

02-16-2009, 06:22 PM
A "gutted" converter will not affect engine coolant temperature. It will however, cause the SES light to come on and most likely a P0420 will be set in memory. A restricted converter is the result of a problem, not the cause, (they don't melt down on their own). An overly rich fuel mixture causes the converter to "melt down" from excessive heat. Before you replace the converter, repair the cause of the rich mixture or you'll end up buying another converter.

Make sure the plug wires are on correctly:

02-16-2009, 06:30 PM
First I had an intake leak and after I replaced all the gasgets I hardly could get it out of the driveway. gutting the cat for the mean time, atleast lets me dive it. I plan on replaceing it with a smaller DIM pipe. Do you think the lack of backpressr has somthing to d with it?

02-17-2009, 06:28 PM
Lack of back pressure in the exhaust has nothing to do with it. If pieces of the converter clogged the muffler, it could cause excessive back pressure, which in turn would cause a lack of power, but not a misfire. Is P0128 the only DTC you're getting?

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