2008 Pontiac Grand Prix 3.8L My car has a P0300 diagnostic code. Check engine light is on, and typically flashes if I exceed about 30 miles an hour. How can I fix this?!

Asked by Nov 30, 2015 at 09:00 AM about the 2008 Pontiac Grand Prix Base

Question type: Maintenance & Repair

I have changed my ignition coils,
cleaned my throttle body, egr valve,
and added a bottle of fuel injector
cleaner into my last tank of gas.
Worked fine for about a week and
started again. It has an occasional
low rough idle, and loss of power.
And has bucked on me a couple of
times. I am thinking it may be a
timing belt issue or a camshaft
position sensor. I am just trying to
figure out my next step. Please
help!!!

2 Answers

17,280

Sounds more like a clogged catalytic converter

42,405

po300 is a random miss fire. First thing that comes to mind is condensation in the gas. Try that red bottle of Heat, something with isophrofel in it to break down any water in the gas. Otherwise with this code would be plugs and wires, but you said it ran fine after the fuel injection cleaner.

Your Answer

Add photo

Related Questions

  • Reduced engine power on a 2008 Grand Prix 75 answers

    I have a 2008 Grand Prix, that worked great until last march when i put it in the ditch. it got all fixed from that. But just this past week i was driving it and it came up with REDUCED ENGINE POWER...

    2008 Pontiac Grand Prix Base

    -

    Maintenance & Repair

  • What is the max milage that a Grand Prix can get? 44 answers

    My grand prix is a 99 and it has 119,000 miles on it. How much longer can it go?

    1999 Pontiac Grand Prix 4 Dr GT Sedan

    -

    Maintenance & Repair

  • 08 pontiac grand prix 3.8 3 answers

    had car for 2 days then while driving the car just shut off everything worked bot wouldn't turn over the next day we messed with it a few min and it just started and ran fine I got car home and shut i...

    2008 Pontiac Grand Prix Base

    -

    Maintenance & Repair

  • Where is the thermostat in a 1999 Pontiac Grand Prix 3.8L V6 1 answer

    I need to Locate the Thermostat on my 1999 Grand Prix, It is over heating suddenly & I was wondering if I could start with a possibly a cheaper fix than taking it in for diagnostics & a new water pum...

    1999 Pontiac Grand Prix 2 Dr GTP Supercharged Coupe

    -

    Maintenance & Repair

Search Pontiac Grand Prix Questions

UK Questions

Are you a UK consumer? CarGurus now has a discussion forum in the UK.

Pontiac Grand Prix Experts

#1 Js08016
Js08016
Reputation 3,870
#2 Tom Demyan
Tom Demyan
Reputation 2,570
#3 munron
munron
Reputation 2,060
View All

Related Models For Sale

Used Chevrolet Impala
935 Great Deals out of 35,463 listings starting at $1,995
Used Dodge Charger
469 Great Deals out of 29,730 listings starting at $2,275
Used Pontiac G8
21 Great Deals out of 463 listings starting at $5,000
Used Pontiac G6
98 Great Deals out of 5,154 listings starting at $999
Used Chevrolet Monte Carlo
13 Great Deals out of 1,701 listings starting at $2,000
Used Chevrolet Malibu
1,123 Great Deals out of 82,795 listings starting at $1,800
Used Ford Mustang
582 Great Deals out of 41,214 listings starting at $1,699
Used Nissan Maxima
413 Great Deals out of 24,330 listings starting at $1,895
Used Jeep Grand Cherokee
1,001 Great Deals out of 65,971 listings starting at $1,500
Used Nissan Altima
1,067 Great Deals out of 82,297 listings starting at $1,900

Used Cars For Sale

2008 Pontiac Grand Prix Base For Sale
11 Great Deals out of 412 listings starting at $900