check engine light

[guz0181]

I have a 2002 blazer that kept giving me the p0304 code which indicated that the 4 cylinder was mis-firing. I change the plugs, wires, cap and rotorand satill gives me the same code and sometimes gives the p0300 indicating multiple cyl mis-fire, I also change the fuel filter and the gas cap clear the code and about 5 min later the check engine light started to blink multiple times on and off. and now the light is back on solid???? can someone help me out of this mess. plz advice...... Rick also it seems to rum smooth i has good pick up at take off and while running!!

[Scrapper]

when is last time you changed o-2's? you say it's running good have you reset the computer again? that miss fire sounds like coil but it cant be i would'nt thank. have you had it anywhere to have them hook machine up to it?

[guz0181]

no I have not hooked to any machine I just check it with the engine decoder at the auto parts store. and no I have not change the o2 sensors. I kind of thought that it might be the coil but did not change that yet thank s for the reply and plz continue to do so
thanks again
Rick

[owens383]

The check engine light is mostly used for just smog is i would start with the o2 sensors.

[blazes9395]

Throw a fuel pressure guage on there and watch for any blips or irregualar moves of the needle. These injectors/poppet nozzles have a tendenancy to stick/clog and cause something quite like this.

[old_master]

I agree, check fuel pressure and leakdown rate. Key on, engine off, fuel pump running, pressure must be 60psi to 66psi. After pump shuts off, pressure must remain above 55psi for 3 to 5 minutes. A fuel delivery problem can set single and/or multiple cylinder misfire DTC's. A faulty oxygen sensor will not cause the SES light to flash, or set a single cylinder misfire DTC.