98deville Posted June 21, 2010 Report Share Posted June 21, 2010 My 2003 deville dts with 98K miles is misfiring bad, the whole engine shakes while parked and idled. I'm also getting the p0300 code, but no check engine light. The front coil pack was replaced months ago with a new one which solved the problem for awile then the misfire came back.I was going to purchase all 8 A/C Delco spark plugs from rockauto and my question was Do I have to change out all the spark plug boots as well, as I would spark plug wires? Link to comment Share on other sites More sharing options...
KHE Posted June 21, 2010 Report Share Posted June 21, 2010 You might want to check the plugs to see if they still have the platinum pad on the ground electrode. What diagnosis was done when the front coil pack was replaced? How long was the misfire problem cured before it returned? Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Ranger Posted June 22, 2010 Report Share Posted June 22, 2010 Check the plenum duct. It's the rubber coupler between the TB and the manifold. Spray some Brakleen at the base while flexing it a bit. If the RPM increases, replace it. Link to comment Share on other sites More sharing options...
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