nearthisbridge

iTrader: (19)

I've been getting an on-again-off-again CEL for a rear O2 sensor and catalyst inefficiency for a month or so.

90% of the time my car starts up by the 2nd crank. Occasionally though (usually when cold), it will sputter for a few seconds and not want to turn over. Eventually it always does turn over though and it runs perfectly after that.

Am I right in thinking that a clogged cat could be the culprit? My gas mileage is still pretty decent (25mpg), so I'm thinking it's probably not the O2 sensor (yet anyway).

Here's a rundown of starting-related stuff that I've replaced in the past:

Coils are about 40k miles old
Plugs are NGK coppers, 6 months old / ~15k
Battery & starter are 1 year old