misfire & vibration

[clifweb]

my 04 bonneville with 3.8 engine sometimes misfires at idle beyond idle runs good,also at idle with ac on it vibrates, wondering what causes these problems and if they may be connected.your help would be greatly appreciated

 

[melsg5]

is your check engine light on and if so have you had the it scanned to determine the code?

 

[clifweb]

Melsg5 the check engine light is not on,so I didn't have it scanned,a little history on the car. It has been sitting up for the past year and from what i understand,wasn't driven much in the past few years before that,I changed engine oil & filter,Trans oil & filter,front engine mount and heater elbows replace coolant that ran out.water leak in passenger compartment repaired splice under front seat to rear doors,thanks to this forum for that information.

 

[melsg5]

when you turn the key to the run position, does the check engine light come on and then when you start the car it goes off? It is hard to believe you have a misfire with no check engine light so I'm trying to determine if the light isn't working. The other possibility is another engine or transmission mount

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[clifweb]

The check engine light does come on then go off when the car starts,from inside the car it sounded like a misfire when i first started it,On the first start today here is what happened,it went to1200 rpms for about 1 minute ,then to 1400,then right back down to 1200 then a minute or so to 1000, then maybe 2 minutes down to 900,then 3 or 4 minutes it was at 750.I tightened the hose form the FPR & evap PV at the TB with a tie tie,I'll report back tomorrow on that,I'll also check that trans mount.