2003 Pontiac Grand Am missfire problem

KRISTY32

MEMBER
2003 PONTIAC GRAND AM
4 CYL
FWD
AUTOMATIC
200,000 MILES

Car was driving fine when one time after I drove it, it started acting wierd, I think it maybe a missfire problem. It is running sluggish until u get over a certain speed, the check engine light is steadly blinking and has a sound like puttering coming from the muffler. I took it to a auto place to put it on a machine they said not to much about some intake thing. I took it to a mechanic to let them listen, they said the samething about the missfire. We changed the sparkplugs but its still doing the same things but only a little, can u tell me what it might be?

Tuesday, October 19th, 2010 AT 12:30 PM

2 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Is it a random misfire or a specific cylinder misfire? Let me know.

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Wednesday, October 20th, 2010 AT 6:05 AM

XTREMEMODIFIER

MEMBER
29 POSTS

Are you 100% it's speed-related, and not RPM-related? Because speed related tends to be vibrations (tire, bearing, driveshaft.) Or noise more than a sluggish condition (typically more of an engine RPM issue).

Since it's an auto, use the lowest gear# lockout (shift it all the way down. Should either lock out 3rd and 4th or 2nd, 3rd, and 4th) then try driving it. BE CAREFUL not to over-rev the engine, and see if it goes away with rpm's.

Did you have the shop write down the exact sensor they diag'd or CEL code they got? How exactly is it sluggish. Just general sluggish (consistant, slow pull) or is it more of a bucking/lunging issue (accelerates then slows repeatedly and quickly)? How is the idle "sound"? Rough? Does the car shake noticably?

How did the old spark plugs look? # Of miles on plugs?

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Wednesday, October 20th, 2010 AT 11:19 AM