2004 Pontiac Grand Am acceleration and bad gas milage

NIPPER5_64

MEMBER
2004 PONTIAC GRAND AM
6 CYL
FWD
AUTOMATIC
174,000 MILES

While cold the car accelerates and runs smoothly has no hesitation. Once it warms to operating temperature it then begins to hesitate at acceleration and runs high rpm's. This is not a consistent problem it doesn't happen all the time. Gas millage is around 17 miles to the gallon. I have already changed the spark plugs, coil packs, fuel filter, ran sea foam through the system as directed, and changed the throttle control sensor. Along with no codes being thrown so now I'm stabbing in the dark what can I do?

3 Replies

MMPRINCE4000

MECHANIC
8,548 POSTS

Check around with autoparts stores and see if they can test the ignition module.

They will generally fail when hot and then when car cools they will work until hot again.

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Friday, April 24th, 2009 AT 7:43 AM

NIPPER5_64

MEMBER
2 POSTS

The hesitation has stopped after I unplugged the egr valve. Now is this the problem or is this just masking another problem. Also the gas mileage has gone up.

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Wednesday, May 6th, 2009 AT 12:09 PM

MMPRINCE4000

MECHANIC
8,548 POSTS

EGR flow at idle or low speeds will cause hesitation, stalling.

It is only supposed to flow at driving speeds and at small amounts, it recirculates exhaust gas'es to intake to reduce NOX formation and will actually reduce combustion temps.

It is controlled by PCM, and will generally set an error code if malfunctioning.

Best first step is to remove it and clean it, (soot buildup) which can cause the metering pintle to stick open, releasing gases when it should not.

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Thursday, May 7th, 2009 AT 5:27 AM