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post #9 of (permalink) Old 06-22-2018
SHELBY GT 350 Member
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Joined: Sep 2010
Location: Houston
Posts: 6,830
Originally Posted by Khenji View Post
oh yea you sent that on the other forum that thing does like very helpful, but what you said makes sense. So it sounds like the best bet is to check for exhaust leaks and replace the o2 sensors? Should I replace all 4 or just the upstream on bank 1 since the code only referred to bank 1? Should I go ahead and replace the cats too?
Note. I haven't advocated for you to change a single part. The operative word here is to TEST/CHECK.

IF there is an exhaust leak the O2 sensors can't work correctly when outside air is allowed to enter the exhaust stream. Therefore the true state of the O2 sensors is UNKNOWN.

Consider that the rear O2 sensors do not affect HOW the car drives. So why replace a part that is not known to be bad? Especially since it won't improve driveability.

Regarding the cats. There's a saying that cats never die. They are murdered. Which means that IF the cats are bad, THEN something caused them to fail. Soooooooooo if you were to replace the cats and did not fix the reason, then you should expect the new cats to fail as well.

Your reply indicated that you did not believe O2 sensors could cause the poor driveability. Those of us that work frequently on our own cars know quite well that O2 sensor problems can cause all sorts of driveability issues. My intent was to give a thought experiment to help you come to your own conclusion.

But don't focus on an O2 problem and ignore any other possible causes for misfires. In general, start trouble shooting with any misfire DTC codes.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.

Last edited by wmburns; 06-23-2018 at 10:37 AM.
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