cat makes rattling noise on 98 accord

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shephard38@insight.rr.com - 11 May 2006 02:54 GMT

For the last three years the catalytic converter on my 98 accord has
been bad according to my dealership. I had them check my car out after
the "engine" light came on. They said it was my cat and it should be
replaced, although I was 9k over the 80k warrenty so I opted to not
replace it. Two days ago a loud rattling noise started to come from
what appears to be the cat. I took the shield off and reattached it in
hopes that the shield was loose. The rattling is inconsistant, ie. no
particular rpm. I live in a state that doesn't test emissions. Would
it be possible for me to replace the cat with a straight pipe? Other
than the obvious law-breaking, what other risks do I run, such as what
do I do with the oxygen sensor and how will it effect my car ovver the
long run?

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Kevin - 11 May 2006 04:09 GMT

> For the last three years the catalytic converter on my 98 accord has
> been bad according to my dealership. I had them check my car out after
[quoted text clipped - 8 lines]
> do I do with the oxygen sensor and how will it effect my car ovver the
> long run?

The catalytic converter has no affect on engine performance and replacing it
with a straight pipe would cause no harm to the engine (we won't get into
proper back pressure for optimum performance here). Now the environment,
that's another issue. Oh, and you might have to get used to that check
engine light, cause with out a converter to tickle the rear O2S, it will
keep coming on till you pull the bulb out.

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Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

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shephard38@insight.rr.com - 11 May 2006 04:53 GMT

So what do I do with the o2s? Do I unplug it or attach it to the
straight pipe? And finally, doesn't the o2s work together with the
injectors for proper performance?

Zeke
"Women find me handsome, but they have never found me handy"
Zeke

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Kevin - 11 May 2006 10:36 GMT

> So what do I do with the o2s? Do I unplug it or attach it to the
> straight pipe? And finally, doesn't the o2s work together with the
[quoted text clipped - 3 lines]
> "Women find me handsome, but they have never found me handy"
> Zeke

The rear O2S is primarily used by the computer to monitor catalytic
converter performance. The front O2S is used for closed loop operation (feed
back to control air/fuel ratio). If you have no CAT you just as well unplug
the rear O2S. Some of the control strategy is based on CAT performance, so I
guess you could say it will affect the engine when the program tries to run
a CAT monitor or if it tries to make up for an always lean CAT. The effect
should be minimal though. I know I have driven cars with a dead rear O2S and
could not detect any engine performance problems other than failed emissions
standards. Maybe just sticking the rear O2S in the pipe would keep the
program happy for everything but the monitor.
P.S. The CAT monitor is that part of the computer program which runs a
check on the operation of the CAT by purposely causing the Air/Fuel mixture
to change and looking for the proper response from the rear O2S. This only
happens under certain driving conditions so it is not a constant monitoring
of the CAT.

Signature

Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green

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