3.4 Cylinder #5 Misfire [Archive] - GrandAmGT.com Forum

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cincydude
05-04-2010, 09:54 PM
2000 Grand Am 3.4L
136,000 miles

About 2 weeks ago I replaced the head gasket and the LIM. While I was at it I changed the plugs(Delco Platinums) wires, thermostat, filters,etc.

The first week it ran like a champ. Then it started to idle rough at a stop and a little as you gave it gas again. There was no SES light so I thought it was a vacuum leak. The hose that goes from the air intake to the back valve cover under the coil pack looked a just a little tiny bit loose so I pushed it back in and it seemed to stop for the next day's work commute.

Today it started again. But this time with an SES light. Took it to Advanced Auto Parts and the read it as a #5 misfire.

So my question is...

Could the plug be too loose or too tight? Faulty? (I checked the gaps)
Why would it take a week to start doing this?

Any help would be greatly appreciated :)