Ive got a 98 blazer 2WD 4DR 4.3 Ive been getting the same code for almost a year now, on and off. Weve already changed to all new plugs & wires, fuel injector, coil, rebuilt the tranny, tried puting new camshaft/crankshaft sensors, but that didnt fix it, we put a new caty converter, replaced the intake seal, the distributor cap, the egr, ect sensor...my dad is a retired mechanic with 30+ yrs experience and even HE'S stumped...at a dead end can anyone shed some light on the situation??...oh and when I accelerate to abt 50-60+ it starts to miss constantly, and whenever I'm driving the rpm with randomly bounce/surge up and down.

 

Is P0300 the only DTC in memory?
P0300 is almost always caused by a fault in secondary ignition. These things are real fussy when it comes to tune up parts. Using the correct parts DOES make a difference.
Plugs need to be AC Delco 41-993 with a gap of .060"
Distributor cap needs to be AC Delco D328A, and use silicone dielectric grease.
Rotor Needs to be AC Delco D465
Wires need to be a good name brand, not a store brand.
Worn distributor gear and or worn distributor bushings and low fuel pressure can also set P0300.

If the crankshaft position sensor or timing cover is moved, removed, replaced, or disturbed in any way, the crankshaft position sensor relearn must be performed. It requires a high end scan tool capable of initiating the relearn. If the relearn is not performed, the engine will start and run, but not properly. The relearn is similar to adjusting base timing.

The camshaft position sensor, inside the distributor, does not affect engine performance. You can unplug it and the engine will still start and run. If the distributor or the sensor are moved, removed, replaced, or disturbed in any way, camshaft retard must be checked and adjusted. This also requires a high end scan tool. Adjusting camshaft retard is done by slightly rotating the distributor. It aligns the camshaft position sensor with the camshaft, hence the name, camshaft position sensor. If camshaft retard is out of spec, it will cause crossfire inside the distributor cap, and the engine will misfire. If the distributor is off one or more teeth, it will set P1345 in memory and turn the SES light on. It can be off as much as ~27 degrees and NOT set the DTC in memory OR turn the light on. The camshaft position sensor data, along with the crankshaft position sensor data, is used by the PCM for detecting and accurately identifying cylinder misfire. If camshaft retard is out of spec, cylinder misfire identification will be incorrect.

Hope this helps.

 

Yeah all the parts we put on are name brand for sure, no cheapo house brands. And a friend of ours, also a mechanic, had one of those $10,000 scanners, andnit was just picking up them

 

Picking up what? Please clarify.

Also, the "name brand" that you installed, was it AC Delco?

 

[QUOTE=La Momia;614060]Yeah all the parts we put on are name brand for sure, no cheapo house brands. And a friend of ours, also a mechanic, had one of those $10,000 scanners, and it was just picking up that the fuel injector was bad/running way to rich, so we put a new one in just a few days later, the problem went away for a few days then came right back! All the parts ive put are Borb Warner, AC Delco, and Delphi.

 

Bad fuel injector will set a DTC for a rich or lean condition, and possibly for a specific cylinder misfire, but rarely a P0300.

Did you perform the crankshaft position sensor relearn after replacing the crankshaft position sensor? It is mandatory, not optional.

Have you checked/adjusted camshaft retard? Same as above, mandatory.

Is the distributor cap AC Delco? If not, you will have problems with it.

 

have u tried the tps (throttle position sensor)? I just did and it seems to be working. first I unplugged it and the idle got better.