2001 Blazer 4.3 The P0300 and yes I have read everything about this code already.

• Runs rough, Shakes like crazy, when about 2000 rpms at about 60 mph it bangs almost like a drive train type issue but just misfires hard. Hard to start. Still gets moving and definitely drivable but gas mpg is BAD. Running REAL rich

• Shows the P0300
• Changed plugs/wires/cap/rotor/fuel filter
• Tried brand new cam sensor / crank sensor / coil / Mass airflow sensor
• No vacuum leaks
• Been at 2 different shops and everybody just shoots at the hip and has no good advice.
• One shop wanted 1200.00 to change spider assembly said it was leaking. Problem is I don't have spider assembly only 2 injectors Another shop said bad cap and rotor but its brand new and nothing got better or worse when it got changed. Went to get Cat checked and told it wasn't my cat.

• So what else is left..... something inside the motor?? So do I get a compression check? What about the MAP sensor? The other thing is when I pull the plug from the MAS nothing changes. Shouldn't it shut off or run a little different? But like I said up top I put a brand new one on and the same thing happened....nothing. Any insight is greatly appreciated....Thanks

 

I'm having the exact same problem in my 01 Blazer and have replaced everything that you have with no luck. I have arching coming from the cap and coil wire even though they are brand new. I'll keep working on it and hopefully one of us will start to get somewhere.

Some suggestions that I have been receiving are to get a fuel pressure test. It may be a fuel pressure problem, either a bad fuel pressure regulator or fuel pump.

 

Never play parts changer to correct a problem. Use a diagnostic trouble chart and follow it. Throwing parts at a problem usually ends up:
1) Not fixing the trouble
2) Installs a new problem or adds another bad part to the mix. (Especially if using cheap after market parts.)

 

Unplugging the MAF sensor shouldn't cause the truck to run poorly. It just goes to default maps in the PCM.

Did you actually try trouble shooting the problem? Have you inspected any wiring?

Someone that knows what they are doing with a scan tool and a good fuel pressure tester can run an injector balance test to determine if the injectors are not flowing properly.

 

Well when you have a friend that works in a part shop and you can go in take what you need, install it and see if it works that's usually an easy way to find out whats wrong.

Everybody I talk to says that when its a P0300 all you can do is shoot from the hip and see what fixes it.....because it could be one of many things.

I havent done a fuel pressure test......t but didn't think that would be it since once it gets moving...... it drives ok except for the occasional banging like the motor just blew up.

And the wiring. Everything looks good, connected, and where it should be.

Well thanks guys I appreciate it!

 

heck if you get parts that easy try replacing the o2 sensors