Hi Jim

I have a 2.1 and have installed a S&S muffler on it. My cat has been
emptied, it's just a place for the o2 sensor now. The rest of the exhaust is
the stock pipes.

I have a perfectly running 2.1, using Digifant. The cat *should* not make
any difference to the running of the FI. It will of course make a difference
to emissions.

My FI troubleshooting started from a similar place to you. I installed a new
o2 sensor, checked my blue temp sensor and made sure my throttle position
sensor was working properly. In my opinion, the most likely culprit will be
the throttle position sensor switch, it's a rather crude affair and any wear
on the throttle body or the throttle stop will cause a maladjustment of the
switch.

Best Regards

Dave

On 14/10/08 10:06 AM, "Jim Johnston" <inmytree1@GMAIL.COM> wrote:

> Hello all,
>
> Vehicle:  91 GL with 163,000+, manual
> Location: Wilmington, NC
>
> I'm trouble shooting a stumbling idle.  I think I've found my problem. I
> noticed the exhaust puffing and the muffler had some odd sounds coming from
> the muffler itself.  So I pulled the cat and muffler.  I only snapped two of
> the three bolts.  It turns out, my catalytic converter has nothing  left.
> It's completely empty.  The previous owner had a S & S Exhaust system put on
> a few months before my taking ownership 3+ years ago.  The cat has big dents
> in it.  My theory is this: when the shop put on the new Header and Muffler,
> they cleaned out the Catalytic Converter.  In NC, vehicles older than 1996
> do not require emissions testing.
>
> I started her up, while a bit loud, no more puff puff puff....
>
> Would running with an hollowed out cat lead to the muffler breaking down?
>
> Now I have to figure out if I have to buy a muffler from S & S or does a
> stock muffler bolt up to the system.
>
>
> Jim
> Wilmington, NC