Rough Idle and Knocking

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Joined: Fri Feb 24, 2017 10:14 am

Rough Idle and Knocking

Unread post by RMax » Fri Feb 24, 2017 10:18 am

I have a 2003 Buick Century 3.1 L engine with 49K miles, has been running great until the other day, went to the store came home everything was fine, but when it was put into park it rev'ed slightly then started Idling very rough, and knocking..
I have replaced the EGR Valve, The Plenum Gasket, Plugs, wires, and all 3 Ign. coils.
I've checked vacuum hoses, fuses, and various connections.
I got rid of the EGR code but still have the P0300 code of Engine Misfire, any ideas what to check? keep in mind everything has been FINE up too when it was put into park the other day, and yes it has not moved since, still idling rough and knocking.....HELP!!! Rick Maxwell Goodyear, AZ.

Also there has been NO Overheating Issues, and Oil is Changed every 3K

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Re: Rough Idle and Knocking

Unread post by carriedi » Fri Feb 24, 2017 11:38 am

you should have it scanned for misfire counter and see what cylinders are affected. Once you can see how many and which cylinders are misfiring you can determine what direction you should go


Re: Rough Idle and Knocking

Unread post by Lagat » Fri Oct 20, 2017 8:05 pm

The knocking sound very well could be a flywheel/flex plate but it should rap at idle. Mine was rapping and thought is was the bottom end of the motor. Sounded very similar. Whats stumping me is it don't do it at idle. I'm guessing the torque converter or transmission. The check engine light never came on?

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