Hello I have a 2001 ZR2 Blazer. I still have a misfire after replacing plugs, wires, coil, control module, distributor, mass air flow sensor, throttle position sensor, air filter. Fuel pressure is right at 58. Trouble code p0300 I sometimes get a flashing check engine light as well. (At times its at idle other times its wgen crusing at around 60mph.)
Rpms Jump up and down at idle and sometime when driving. Runs better when cold. Blazer has 206k miles. I have had it for about 2mo. Any help would be appreciated.

 

the 0300 is multiple cylinder misfire. What type of cap and rotor do you have, these trucks are fussy about that. Use only acdelco cap rotor and wires. Flashing check engine is high amount of misfires.

 

It's a brand new duralast distributor with cap and rotor.

 

 

After distributor was changed all was good for a few days.

when driving all is good for about 15 min of freeway driving then the rough idle starts.

 

 

Yes it does seam to correlate with the coolant temp.

and i have not tried the pressure test when it was rough. (will see about trying this today).

 

If you have live scan capability, see it it gets rough after the fuel system goes from open to closed loop.

George

 

Most problems are a cause of something done recently, I would put an ac delco cap and rotor on and take off the garbage

 

did a pressure test when it was hot. Fuel pressure (running) was 52psi. Also when driving on freeway and when let off the gas from around 65mph i can feel it missing.