The engine has been running rough at idle for a while and the tail pipes
have been a little dark as though it is running a bit rich. It failed
the smog test on NO.
I will be changing the plugs tomorrow and starting the check of the
other laundry list of things that might be wrong, but the guy who wants
my money just keeps saying it is the catalytic convertor.
Well, it could be the cat, but you need to look for air leaks in the
intake system, including all the hoses and tubes, first. The cat
is the *last* thing you should replace. A plugged cat may indeed
cause similar symptoms to intake system air leaks, but a good
mechanic should be able to diagnose these problems separately.
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