2005 Grand Prix SE. poor fuel economy and power loss

[rogerwc]

I have a 05 Grand Prix SE with a 3.8
I have an intermittent problem with power loss and really poor fuel economy. No check engine light. The problem will go away and perform normal then come back again a few days later. I have tried
injector cleaner, sea foam intake cleaner, tune up(plugs,wires) brought car to dealership they couldn't find anything wrong said they cleaned the throttle body.
After I got the car back it was fine for about 2 weeks. Any ideas??

[GTP Dad]

Welcome to AF!!

Loss of power can come from a lot of issues. Did you change the fuel filter when you changed plugs and wires? Another issue to check would be the oxygen sensor. It may be going bad but not setting a light since it is intermittent. The sensor i am speaking of is the sensor in front of the convertor. This can account for the poor performance and decreased fuel economy.

[rogerwc]

Originally Posted by GTP Dad

Welcome to AF!!

Loss of power can come from a lot of issues. Did you change the fuel filter when you changed plugs and wires? Another issue to check would be the oxygen sensor. It may be going bad but not setting a light since it is intermittent. The sensor i am speaking of is the sensor in front of the convertor. This can account for the poor performance and decreased fuel economy.

Could not change the fuel filter. I was told that is not serviceable since it is located inside the gas tank and part of the fuel pump. I will look into the o2 sensor. Thanks

[roman1978]

i have the same problem with 05 GTP have replaced plugs wires and problem still there its happens sometimes not all teh time. no light eather. last time i had the car scanned showed missfire.

[olopezm]

Even when the problem didn't seem to be solved for the original poster this applies for both of you guys.

Check the air filter and also clean the MAF sensor, use only approved MAF cleaner or electric contact cleaner both available at autoparts stores. Only spray the sensor and DON'T touch it.

The misfire can be caused by several things, clogged injectors; bad plugs, wires or coils; vacuum leaks; worn/damaged rings or valves; a dirty or bad MAF.

You can try unplugging each injector with the engine running and there should be a slight difference in RPM's if there isn't then you've found a dead injector.

Oscar.