99 s10 4.3 p0306 misfire Need Help

ChrisInLA · August 25, 2006

I have a 99 s10 vortec 4.3, I've had a P0306 misfire code for months. I started with Tune up parts, Delco cap and rotor, delco wires delco platinum plugs. All original equip. Truck still misfires. Tossed K&N filter and cleaned the MAF, and throttle body. No help. Removed the CFI fuel injector and bought reman. Truck runs better but still misfires. I need help diagnosing either the pickup coil (cam sensor) or Crank pos sensor. Anyone know a test procedure or a better Idea? I'd appreciate any help thanks Chris

95Sierra2500 · August 25, 2006

I don't know about the test procedures, but did you get new poppet nozzles with your injectors? If you didn't, I'll bet that's your problem. The other problem could be a fuel pump, but usually it won't start before it exhibits these problems.

ChrisInLA · August 25, 2006

No new poppets but I did watch it be rebuilt, the spray pattern before was horrible but it looked great after rebuild, I've also replaced the fuel pressure reg on the cfi unit. And i've got between 52-54 psi fuel pressure..... I'm going to pull distributor today and check pickup coil. Thanks for the input

95Sierra2500 · August 25, 2006

Another thing I just thought of (tho we were throwing P0300 random misfire), but how many miles are on your catalytic converter? That turned out to be one of many problems. Original cat went bad at about 128k, put in a new one and it was clogged by 135k (damned autozone parts). If this next one gets clogged again, we're going to Muffler Man and buying one the next size bigger, I've heard this takes care of the problem.

ChrisInLA · August 29, 2006

still knocking any ideas?

95Sierra2500 · August 29, 2006

No new poppets but I did watch it be rebuilt, the spray pattern before was horrible but it looked great after rebuild, I've also replaced the fuel pressure reg on the cfi unit. And i've got between 52-54 psi fuel pressure..... I'm going to pull distributor today and check pickup coil. Thanks for the input

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That actually sounds a tiny bit low. I think they're supposed to have 65 psi w/the truck off, and 55-57 with the truck running...