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Thread: Vibration at idle under load

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    Angry Vibration at idle under load

    Hey everybody, I have an '04 malibu classic with the 2.2L and...my dashboard likes to vibrate at idle, specifically when the car is in drive, a/c is on, and brakes are applied, put all 3 of those things together and the dashboard shakes like an evinrude. I replaced the forward motor mount and then played with the adjustment setting, then cleaned a very dirty Idle Air Control valve. I *hoped* that those fixes would be enough to stop the jitters, but in reality they did very little. the car has no vacuum leaks, no trouble codes, and the engine itself runs quite smoothly. it's perfectly behaved above 800rpms and I'm kinda at my wits end trying to find a fix for this problem.

    Is there anyone else out there who is familiar with the problem?

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    Maybe someone knows a way to increase the idle 50 rpm's or so?

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    Did you inspect the rest of your motor/transmission mounts?

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    I'm assuming there are three more drivetrain mounts. One on top of the transaxle, another under the exhaust manifold, and a mount on the passenger side near the top of the engine. Sounds like the bushing in the rear transaxle mount (one under the exhaust manifold) is shot. That mount usually goes the quickest because of all the heat from the exhaust manifold a short distance away from it.

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    I have inspected the 3 most visible mounts, and while the rear one *looks* okay, I haven't eliminated the possibility that it might have hardened up over the years. It certainly doesn't move when I shift the car from neutral to drive. I'd be willing to give it a shot since the part is only $35, but without seeing any movement in the mount?

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    the hot idle on this car sits around 600rpms, that's a little low isn't it?

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    Don't touch the throttle stop(FYI). Did you just change the plugs? AC or NGK are the ones that work well, others may cause problems.
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

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    Don't touch the throttle stop(FYI). Did you just change the plugs? AC or NGK are the ones that work well, others may cause problems.
    nogo04cav Quoted Post
    They're Bosch plugs, I changed and indexed them about 30,000 miles ago but they still look good, no unusual discoloring and zero carbon buildup, the previous plugs were Denso brand, I still have them because they looked so good. Neither brand did anything to change the vibration I'm referring to. Are these engines that finicky about plugs?

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    Yes they are a bit finicky. Can you have the ICM tested?
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

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    Yes they are a bit finicky. Can you have the ICM tested?
    nogo04cav Quoted Post
    I just tried some new ACdelco plugs, no change in performance. The ICM is the metallic object with cooling fins on-top of the coil pack correct? I bought a second coil pack shortly after I bought the car, and subsequently a new ICM, neither the new one nor the old one caused any change.

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    600 is the proper idle for an automatic. If you're not getting misfire codes, I wouldn't suspect the plugs or ignition (although it isn't impossible). How many miles are on the motor and are there any codes, even pending, if a scanner is plugged in? If there are no codes or pending codes I might suspect the water pump chain may have slipped. There are 2 timed balanced shafts on with the water pump that are supposed to oppose the natural vibrations of an inline motor.

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    Unhappy

    600 is the proper idle for an automatic. If you're not getting misfire codes, I wouldn't suspect the plugs or ignition (although it isn't impossible). How many miles are on the motor and are there any codes, even pending, if a scanner is plugged in? If there are no codes or pending codes I might suspect the water pump chain may have slipped. There are 2 timed balanced shafts on with the water pump that are supposed to oppose the natural vibrations of an inline motor.
    Sparkey Quoted Post
    there's 184000 miles on it, so I wouldn't be surprised if that was the problem, how do I check on the chain, is there an inspection plate somewhere I can remove? I might just pony up the money and have the dealer do it if it's too big a job for my toolset.

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