Date:         Sat, 13 Apr 2002 14:42:33 -0700
Reply-To:     Graham Freeman <graham@CALTEG.ORG>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Graham Freeman <graham@CALTEG.ORG>
Subject:      Re: '85 Vanagon fails smog - diagnosis help requested
In-Reply-To:  <000201c1e327$f690d0c0$6202a8c0@dadspc>
Content-Type: TEXT/PLAIN; charset=US-ASCII

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