Q: Engine knock and hesitation

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I noticed my engine seemed to to shaking more than normal when in reverse and especially in drive along with poor acceleration. Also check engine light was on and then it started flashing. One diagnostic reading showed multiple misfires and catalytic converter. A second showed the mass air flow sensor. I also noticed that the exhaust manifold converter was fire poker red one morning and I was told that my converter was clogged up. I had the exhaust manifold changed but my car seems to still be doing the same thing. Only difference is that the engine knocking is a little less. What's going on? Any info would be appreciated. Also I had the spark plugs changed. And upon changing those I noticed a little oil around one of the ignition coils and was told that the valve cover gasket was the root of all my problems. I'm lost!!!

My car has 221000 miles.
My car has an automatic transmission.

The poor acceleration and misfiring can definitely be tied to the[clogged catalytic converter, but something had to clog the converter. In many cases, oil entering the exhaust or too rich of an air/fuel mixture can overwork the catalytic converter to the point where it cannot burn off the extra oil and fuel. Your vehicle may be equipped with multiple catalytic converters, one on the exhaust manifold and another further down the exhaust plumbing.

Both catalytic converters must be replaced if one fails. The converters, spark plugs, and valve cover gaskets must all be replaced to correct the situation. Have an experienced technician, like the ones we employ here at Your Mechanic, inspect the vehicle to further diagnose your Check Engine Light and to see if there is another underlying issue like a failed ignition coil or stuck open fuel injector.

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