On Sat, 13 Apr 2002, Dennis Haynes wrote:

> With readings that high, the catalyst is not your only problem. The cat
> is a clean up device, not gross pollution prevention device. You don't
> state what the CO (carbon monoxide) reading is. This would be very
> helpful to help with a diagnosis. You need to check for the following;

The C02 readings are:

idle (978rpm): 9.38
2500rpm (2636rpm): 11.52

02 readings:

idle (978rpm): 7.5
2500rpm (2636rpm): 4.1

C0 readings:

idle (978rpm): 0.35
2500rpm (2636rpm): 0.82

> 1) Engine condition. Good compression. Intake and exhaust valves sealing
> properly. Leak down test would be best indicator.
> 2) Ignition, make sure there is no intermittent miss fire. Have shop
> test with a scope if needed.
> 3) Vacuum leaks, bad injectors. Either condition can cause 1 cylinder to
> miss fire, (lean-miss). This will cause high HC.

I'll have these three looked at.

> 4) Fuel mixture, what is the CO reading? Should be between .2 and 1.0%,
> before or without the CAT.
> 5) Basic engine settings. Make sure the timing is set to spec. Over
> advancing the timing can cause high CO readings, particularly at idle.

It looks like these two are no an issue, correct?

> You need to get that HC reading down to at least 1/2 of what you have
> before replacing the Cat. Otherwise you will burn up the new one.
>
> Good luck,
> Dennis

So, it sounds like I'll definitely need a new cat, but not until the other
work is done first...?

Good info.  Thanks!

-Graham