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Chevy, Chevy Mechanic
Category: Chevy
Satisfied Customers: 451
Experience:  15 Year as an auto mechanic and technician.
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2001 Chevrolet Blazer 4.3, code p0300, starts and runs fine

Customer Question

2001 Chevrolet Blazer 4.3, code p0300, starts and runs fine @ idle and light acceleration n no load.. throws code n misfires under load or higher rpm, or heavy acceleration....

under heavy acceleration it will almost redline before shifting.. normal driving under 35 mph in town--no codes or misfires..

NEW-cap,rotor, plugs, wires, air and fuel filter..

I noticed this a few weeks ago, checked codes.. cleared it.. then took it out for a drive.. code didnt come back on or misfire untill under hard acceleration.. today i put all new parts on listed above.. cleared codes... ran fine untill under heavy acceleration...then back to same story of P0300 again.

you wouldnt know nothing was wrong with it under light to normal acceleration and driving around town..

Im tired of sticking money into it and running outta time.. have a 1000 mile trip I have to make this wknd to go to my aunts funeral n dont want to stall out...
Submitted: 8 years ago.
Category: Chevy
Expert:  Chevy replied 8 years ago.
HiCustomer.. here is a list of things that it could be. I'm sure you've eliminated some of them but here it goes....Click on the View Image.

graphic
Customer: replied 8 years ago.
everything seems to check out... like i said i just put new dist cap-rotor-spark plugs-rotor-plug wires, and fuel filter... there are no vacuum leaks or anything plugged... i also dumped a cpl cans of fuel injector cleaner in there too and nothing has seemed to help yet
Expert:  Chevy replied 8 years ago.
Did you happen to notice what color the plugs were when they got changed?
Customer: replied 8 years ago.
they were more on the gray to white side.. lean rather than rich or carbon build up..
Expert:  Chevy replied 8 years ago.
I'm leaning towards clogged fuel injectors. Have you tried replacing any?
Customer: replied 8 years ago.
correct me if im wrong but doesnt this 4.3 have the spider injector set in it where its all one unit or set.
Expert:  Chevy replied 8 years ago.
I believe your correct but apparently it's running lean and not giving you the power you demand.
Customer: replied 8 years ago.
It did pop codes of p0131 and p0151, which is the O2 sensors bank 1 and bank 2.. it was running worse now this afternoon, checked and cleared codes and now seems to be running fine again.. Not sure what is going on being that it is now intermittent..
Expert:  Chevy replied 8 years ago.
Those are lean codes but it's unlikely that both would go out at the same time.
Customer: replied 8 years ago.
yes thats wat i figured, but once i cleared codes its running great again.. gonna go take it for a lil ride again here and see what it does.. hope its done with its attitude because have a 1000 mile trip to take off for in the morning

Ill let ya know what it does
thanks
Travis
Expert:  Chevy replied 8 years ago.
Keep me posted...
Customer: replied 8 years ago.
Good Afternoon,
Well the Blazer ran tip top shape after cleared codes, and also put both O2 sensors in before took off for 500 miles, no problems, missing, or lack of power..
Then started acting up again on the way back home for about 300 miles, had to keep gas pedal to the floor and could barely get 75 mph out of it.. was acting same way prior .. then last 200 miles it started running a lil bit better again and finally started running great again once got back home...
Expert:  Chevy replied 8 years ago.
I forgot to give you my condolences and I'm glad the truck ran fairly well.
Customer: replied 8 years ago.
Thanks, XXXXX XXXXX on what to check again.. What is the fuel pressure suppose to be at.. gonna check that at fuel rail.. not sure what else to check.. unless its bad injectors but havnt had them act up n then run perfect again.. most of time ive had them go bad that they act up and run shitty.. not come and go like it has been..

any ideas
Thanks
Expert:  Chevy replied 8 years ago.
The fuel pressure should be around 55psi during idle.
Did you say you checked the filter?
Customer: replied 8 years ago.
ok thanks, XXXXX XXXXX the pressure checked and back to you, gotta find my guage first.. lol

Yes new fuel filter installed too
Expert:  Chevy replied 8 years ago.
Keep me posted... it helps me too!
Customer: replied 8 years ago.
fuel pressure is good, what next
Expert:  Chevy replied 8 years ago.
How about the PCV valve...
Customer: replied 8 years ago.
PCV Valve is also good.. checked that right away last week when was looking for vacuum leaks
Expert:  Chevy replied 8 years ago.
I got my letters mixed up... the PCV valve would give you back pressure.
I should of said... how about the EGR valve.
Expert:  Chevy replied 8 years ago.
I got my letters mixed up... the PCV valve would give you back pressure.
I should of said... how about the EGR valve.
Customer: replied 8 years ago.
It should be good, I havent taken it off yet.. but it was replaced cpl months ago.. and all carbon build up etc was cleaned out of intake when new one installed..
Expert:  Chevy replied 8 years ago.
Do you mean the intake manifold was removed and cleaned?