So i've got a 96 blazer 4.3 that has been running pretty strong since i bought it a few years ago. It has 131,000 miles on it. A couple weeks ago I started it up to go to work and it idled and started fine, then I started to drive to work and it imediatley started to spudder really bad and then made a loud pop (backfire). It has been running like this and seems to be getting worse ever since. The check engine light comes on for a while then turns off even thou it is still running very rough. At one point it was flashing meaning multipul cylinder missfire but has one done it once. Fuel filter done less than a year ago, did cap and rotor (haven't done wires yet) in summer, O2 sensors a year ago, 3 part fuel injector and intake cleaning, and new catalytic converter 5 months ago. Anyone have any idea why it would suddenly start to run like this? Possibly extreme Minnesooooootaaah weather? Moister in distributor? Bad fuel pump of spider injector? Bad coil? Bad timing chain? Leak in intake gasket? Any help would be apprieciated.

Thanks!!

 

I would start by cleaning the MAF sensor and EGR valve (search).

 

Ok I cleaned the MAFS and still need to do the EGR. Is the EGR on the front of the intake? How much can a bad/dirty EGR effect how the engine runs? Its been running a little bit better since I cleaned but still sputters a little bit. Any other suggestions?

Thanks!