Hey guys got a 2000 blazer 4.3 4x4 with 156000 on it and out o the blue today it starts missing in overdrive and if you put it in park or neutral and rev it, it misses at low rpm. If your driving and it starts missing you can drop it into 3rd gear and it will stop missin. it's like it misses under low rpm with a load. I had to put lifters in it about a year ago so I went ahead and replaced all gaskets, plugs, wires, cap, rotor, and yes I fell victim to the aftermarket cap and rotor (must be a AC Delco cap and rotor),also replaced all filters. I guess my question is could my plugs all ready be fried or my cap and rotor they have about 15000 miles on them. Thanks

 

i have autozone cap n rotor

 

Your lucky then,, most after market are not poured right and it will cause a miss,, I spent 3 hours once checking a friends GM V-6 was running greta until he tuned it up,, a slight miss but it was there,, compression ck ect,, bought a GM cap/rotor and still today runs like a champ,,

Zman,, cap I would say no but,, at night in a dark area lift your hood while it is running and check for arching from the plug wires,, also pull a couple of plugs just to check what they look like,, also check vacuum leaks,, what kind of plugs did you put in?? Matty man

 

get your hands on a inductive timing light, you can use that with the engine running to see if your getting rhythmic spark to each cylinder without getting zapped or taking anything apart. if losing spark, check at coil wire at idle if steady you know its in the cap/wires, if misses at coil then coil or sensor breaking down. a scanner with data stream would be worth gold in this case. i would also suspect a egr carboned up and not closing fully or a leaky injector. but def check ignition first...

 

At matty man no there isn't any arching at night checked that last night. At trucktom ill check the coil today my wife is driving the truck now so gotta wait til she gets home. You know I have had nothing but problems with the ignition system on this truck. ill keep u guys posted