Close
Car Questions
RepairPal is your advocate for car care advice and guidance

P0171 & P0300, Fuel lean, random misfire.

(2001 Pontiac Grand Prix)
in Virginia Beach, VA on April 12, 2011
Here is a run down of the problems. Listed as running lean I have a fuel pressure of 30psi not the 48-55psi required. all lines checked and good. Fuel pump is good. Have been told that the piston rings may be out and need replacing. Also got told that problem might be in the fuel injectors may be clogged, but wouldn't the lines be over pressure if at the end of line. However car starts fine when cold. Will not start when hot or has been running for more then 30 minutes, car must sit for an hour at least to be restarted. Makes chugging sound when initally started then evens out. Also car shimmies at 42mph and 74mph. No idea why the shake but rides fine at any other speed, odd.
Displaying 2 answers & 0 comments
Popular Answer
on April 12, 2011
I agree with Jim. I bet the pump is bad. that is the reason for not starting as the fuel pressure is too low and the fuel is very hot and almost boiling.
this is also the 171 code and the 300 code.
the shimmy may be wheel balance or a shifted belt in a tire. have it checked at a shop.

thanks for using repairpal.

Roy
on April 12, 2011
You must determine the cause of your low fuel pressure. I would strongly suspect the fuel pump or pressure regulator. If you can find a way to block the fuel return line and the pressure does not go up then the problem is with the supply side - fuel pump or available voltage to it. If the pressure rises with the return line blocked (in should go over spec) then chances are the fault is with the pressure regulator. With the fuel pump running and the engine off the fuel pressure should he 53-59 psi for the standard 3.8L and 48-54 for the supercharged version.
RepairPal estimates are guaranteed at over 2,000 quality certified locations nationwide. Learn more

Similar Questions

View answers to similar questions from RepairPal's community of auto experts and enthusiasts.
I was having P0171 & P0174 codes for Air/fuel to lean. Saw where Mass Airflow sensor is normal cause. Changed the Sen...
Catalytic converter was stopped up replaced it and it runs fine for a little while and then my check engine light sta...
Didn't find what you were looking for?