dreaded p0300

[96_blazer_5spd]

i have seen a couple threads in here about this same problem and i have dealt with it on another blazer, now mine ( a 96 s10 blazer) is doing it and i still cant figure it out. in the last 5,000mi i have replaced my coil, cap, rotor, plugs, wires, fuel pump, spider injection, all ac delco. about a week ago i was driving, engine running great in the sleet/snow. turned the car off and let it sit for about 5 hours and when i started it up i was misfiring on cyl 3 and 4. now im starting to miss on 1 and 2 as well not as much but still... I have switched wires and sparkplugs between 3 and 5 and 5 still hasn't missed once. my injector ohms at 12 for all cyl, fuel pres. stays around 60, anyone have any fresh ideas for me to try?

[Chris Stewart]

Does it have the CPI fuel injection..."W" code?

[96_blazer_5spd]

yes it does

[Chris Stewart]

Just did some checking, the '96 has the Sequential Central Point Injection(SCPI) like the '97 has.
Looks like you've changed nearly everthing and the only thing I see left is the fuel filter, Crankshaft Position sensor (CKP), the Mass Airflow Sensor (MAF) or a dose of bad gasoline.
A fuel pressure test will help show a bad filter...with the gauge connected and engine idling, the fuel pressure should increase when you stomp (and quickly release...don't overev the engine) the accelerator pedal to rev the engine up.
Here's where you check the fuel pressure...

[96_blazer_5spd]

i found a junkyard scpi fo 16 bucks and figured even if it was not the problem i might be able to make a couple of bucks off it. i also replaced the plenum gaskets and this seems to have fixed the problem. just another case of a new part (from craigs list) gone bad.