MY 2000 blazer sat in a shop for a week or more getting the axle and transmission diagnosed, when I got the car back it was running very, rough, sounded like it was running on 4 cylinders. I hooked up a scanner and got a 0300 random misfire code. The tech said all he did was put the car on a scope to diagnose the tranny and axle. It has steadily gotten much worse. stuck egr valve? fouled plugs? Any ideas, I don't want to sink too much into it, turns out the axle is shot and needs replaced. I'd like to at least getting it running smooth again before I try to sell it... BTW, the local junk yard didn't even want to buy it, but I digress.

 

common fixes for this problem, though it sounds like you might need some heavy duty scanners for most of these

1. Check the cam retard offset and adjust to 0 if off by 7 or more degrees. Grind the distributor hold down clamp to allow adjustment of the distributor.

2. Check the injector balance and if bad injectors are found, consider updating to the new style injectors per TSB #00-06-04-003B.

3. Check the Bank 1 Sensor 2 (B1S2) O2 sensor (just in front of the catalytic converter) wiring and connections.

4. Compare the Bank 1 Sensor 1 (B1S1) and Bank 2 Sensor 1 (B2S1) O2 sensors to the B1S2 O2 sensor, and if the B1S2 is reading differently from the other two, replace the B1S2 O2 sensor.
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p0300 can pretty much be anything. we had a acura come in the other day for a p0300 along with 4 different cylinder misfire. car ran pretty good, coils all worked and spark plugs were fine. after looking around the engine i found the vacuum hose for the fuel pressure regulator was knocked off. that fixed the problem