P0171, P0300, P0306 97 Pontiac Grand Prix GTP

After purchasing the car, while driving it home, the general conditions for the P0171 occured(loss/no power, knocking, stalled) Purchased a scanner and got the codes, followed the usual steps. The preculiar thing is that the code 0171 and conditions only occur after the vehicle has been run for atleast 15 minutes, parked, then re-driven. The first run off the day, no matter if morning, noon or night always goes smooth. I have also noticed a "ticking" in the top of the engine prior to the "engine malfunction". I have seen posts where the intake gasket may be a culprit and by having the supercharger, would this make the condition worse? There are also times that after an initial hesitation, sputter, misfire....the engine will operate smoothly. One thing that occurred this evening that baffles me.....car left the stoplight normal and crused up to 55mph without hesitation, but when I "put the pedal down" to pass a vehicle, the RPM's went up 1500, the supercharger spooled up, but the car failed to accelerate and acted like it was in a "suspended animation" and did absolutely nothing. After coming to a complete stop on the side of the road, the car once again accelerated fine. No codes and no MIL. Fuel pump now seems to have a whistling noiise too.

backpressure?

I would assume that the backpressure being refered to is the fuel. I haven't checked the fuel pressure as this whistling has started just last night. The codes started 2 days ago. I will check the fuel pressure today. As for any other backpressure, would the EGR or any other system cause the 0171 and symptoms? I only have a Actron code scanner, and not a all out system monitor. What is the safest way to check the fuel pressures?

"Backpressure" meaning a restriction in the exhaust system. Normally it is either the catalytic converter or the muffler that is plugged, but check the entire exhaust system.

First test would be with a vacuum guage.

For checking fuel pressure, use a quality fuel pressure guage hooked up to the shrader valve. Check pressure against specs. at KOEO, idle and watch for any bleed off.

Good luck and keep us posted.

Just thinking.....car starts and retarding/misfiring occurs after initial sensor timeouts(15-30 seconds). I have had a 1999 and a 2002 GP and never experienced this problem. Now, thinking of the events that happened prior to the current P0171 and the previous owner not having this problem ever.....I filled the car with the required 91 Octane or higher fuel, 93 to be exact. Now, in thinking about the car and all of the warnings about running lower octance fuels and the pre-ignition that occurs with lower octane fuels with the supercharger...I might begin to think that maybe I received 87 octane from a 93 pump. The only code is 0171 and when you press the gas and it stutters/shutters, misfires as the timing is adjusted electronically, it might make logical sense...Right?

Please note....after careful consideration and thought, put 2 containers of Champion Octane (15 points or 1.5 Octane per 21 gallons) booster into tank with remaining 6 gallons of gas, plus 5 gallons of 93 Octane fuel and car operates like it is brand new. Shutters when starts in sensor bypass breifly, then smooth sailing. Last Thursaday, pumped 14 gallons of fuel from a 93 pump, got probably 87. 5 days later and countless hours of work and lost sleep due to some IDIOT FUEL TRUCK DRIVER putting the wrong octane in the station tank. All I have to say to the driver is THANK YOU FOR NOTHING!!