2003 zr2 4.3 blazer having trouble with p0300 misfire code. It has been running pretty good besides slight miss now and then but tonight it started surging on the highway at about 70. It would lose rpms then rev back up. It kept surging even after i slowed down. Got it home and tested fuel pressure. Up to 55psi when key turned engine off and slowly dropped to zero after about 8 minutes. It has new plugs new wires new distributor and cps and has had a relearn done on it. I decided to pull the intake manifold and found the whole intake to be wet and clean not black like i expected. I reconnected fuel lines and turned the key to try ad find a leak. Nothing from any injector or from the fpr. Number 6 intake channel is completely full of fuel. It has also has a new mpfi system installed by the previous owner. Any help is appreciated im thinking possible bad injector or icm. Thanks guys

 

 

Howdy,
A good place to start is to check the fuel trims. It should give a bit of understanding why Your injector is flooding. It might be over-regulated in the process calculation.

 

Alright i believe i can watch them on torque pro so ill look into that but can anyone tell me what some normal trims would look like?

 

Normal trims are below +/-10%. It could vary in range of -3..+3

 

Shrtft1 varies from 0 to .8
longft1 3.9
shrtft2 varies from 2.3 to 4.7
longft2 .8
i hope this helps im not sure what they mean

 

So after replacing ICM and MPFI i cleared the codes and drove it again. After about 5 minutes of easy driving the ses light was flashing and threw the p0300 code. If you step on the pedal while the lights flashing and let it get going the light goes off. Comes back on after easy driving again. At a total loss with this blazer.

 

... please post ST/FT for idle and for 2500 rpm. Was it running fine after replacing the cap/rotor or the problem came out right after?

 

No the problem occurred before cap and rotor. Im going to put brand new plugs and wires and compression test then ill post fuel trims at 2500

 

Idle st bank 1 0%
Idle st bank 2 0%
2500 rpm st bank 1 -12.3%
2500rpm st bank 2 -11.8%