I have a 1999 Chevy Blazer, the check engine light (p0420 - catalyst efficiency below threshold) came on about 6 months ago. A mechanic told me not to worry about it. This morning the engine starting missing and a new code appeared (p0303 - cylinder number 3 misfire). I replaced the plugs and wires but this did not fix the problem. Is this all due to the catalytic converter?
Most probably and if a cat is not flowing proper is causes back preasure that can result in sticking or burned vavles,mechanic not nice by saying ignore the cat effiency code p0420.Can ussually have cat replaced at aftermarket muffler shop for approx. $200 cheaper than valve job or excessive fuel that you have used and damage that may occur to your engine.
My 98 gmc gimmy has cylinder misfire and run rough
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