I need help I have just purchased a 2001 chevy blazer 4.3 with the "w" vin and I have a code PO300 which I know is a multipal cylinder misfire.

Now I have read some other post about this same code with the exact same vehicel but with slight changes in problems (which are) easy start ups when cold but it struggles when warm and it runs rough when idle but not with a load (driving at any speed/ rpm).

Now the fuel pump has been changed (was told that it was magicly going to fix everthing but Im not that stupid), checked / changed the pcv valve (smelled like gas), pulled the #1 spark plug not fouled but smelled like gas (I have not had time to pull all plugs since I work and go to school but will check with in the next week), and heard slight spark possibaly like arcs of electricity but not to sure.

Im not a mechanic but I know somethings. If I could get some help with this I would be much obliged.

 

Get a fuel pressure reading under the hood at the schrader valve, and that will be a good start to determine if you've got a fuel issue. There is a regulator under the intake that is part of the spider injector assy as I understand it. If that is failing out, you may be pouring fuel into the cylinders from the sounds of it.

I have not dove into that side of the fuel system myself, I had a very old and restricted fuel filter on mine that much to my surprise fixed my issue before I had to get into the system further.

If you do a search or dig around some, you'll find more information then you know what to do with here on the fuel systems.

What did the plugs you pulled look like color wise at the electrode?

Also, what exactly are the symptoms YOUR truck is having?

 

First step - complete tune-up if not done recently. New distributor cap and rotor, plugs, fuel and air filter, perhaps new plug wires.

 

I have read about the regulator, just haven't checked want to get the book for the blazer.
As for the plug it looked normal no carbon just a slight smell.
I'm just waiting for pay day to do the tune up.

 

Ok I am back I finally did a tune-up still same problem, but I also did a fuel pressure test
with the key on engine off it went to 60 psi then shot down to 50
when I turned the key off it went down to 40 in about a min or 2
could that possibly be the fuel pressure regulator any help would be great thanks

 

Work through all the steps in 96+ Fuel System Diagnosis to isolate the problem.

 

well I finally removed the plenum and turned the ignition to run and saw that the fuel pressure regulator was leaking slightly so I replaced it, low and behold it was the culprit, put it all back together turned the blazer on let it run for a bit then thats when the check engine light turned off. I took it around the block turned it off then back on and it started right up with no hesitation.