MISFIRE 3 CYLINDER SHOWING CODE P0303 -CHECK ENGINE LIGHT FLASHING -COIL IS GOOD - SPARK PLUG HAD FRESH OIL ON IT WITH CARBON BUILD UP -CHANGED SPARK PLUG AND STILL MISFIRING -TOOK VEHICLE TO THE DEALERSHIP AND REFERRED TO TSB-13-082 V6 MISFIRE EXTENDED WARRANTY - MECHANIC STATES THAT IT MIGHT BE A TIGHT VALVE AND MAY BE BURNT. MECHANIC USED A BORE SCOPE AND NOTICE VALVE ISN'T SEALING PROPERLY. MY VALVES WERE ADJUSTED AT 106K LAST YEAR JULY/AUG. IF IT WAS DO TO A TIGHT VALVE WOULDN'T IT THROW A CODE THEN?
-CAN BAD PISTON RINGS CAUSE A VALVE TO GO BAD?
My car has 115000 miles.
My car has an automatic transmission.
Hi There, There are several reasons that can cause a valve to burn. One is normal wear and tear. As miles are put on an engine, the constant pounding and heat erosion wears away the metal on the face of the valve and seat. The exhaust valve sheds most of its heat through the valve seat in the cylinder head, so when the face and seat become worn and the area of contact is reduced, the valve starts to run hot. Eventually the buildup of heat weakens the metal and pieces of it start to break or flake away. As this happens it can form hot spots that even speed up the process. As the valve begins to leak and compression drops, the result is a weak or dead cylinder and a noticeable drop in engine power and performance. A bad exhaust valve will also increase exhaust emissions by a considerable amount because it allows unburnt fuel to leak into the exhaust. Thus, high hydrocarbon (HC) emissions may also indicate a burned valve. Valve burning can also be caused by any condition that makes the engine run hot or elevates combustion temperatures. This includes cooling problems, abnormal combustion like detonation or pre-ignition, loss of exhaust gas recirculation (EGR), retarded ignition timing or lean fuel mixtures.
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