Thanks Dennis,

I replaced the cat last smog check,   eg 2 yrs ago,   and the O2 sensor
18 months ago. Could the cat burn out so soon?

Last time I pulled plugs and replaced and checked compression.(3 months
ago) I got the following:
**Note This engine has a lot of miles on it and these values seem low
but it is still running "OK".

1)   100
2)   100
3)   120
4)   120

(20 cranks engine cold with a snapon gauge)

-john

Dennis Haynes wrote:
> The fact that your CO reading is the same at both idle and 2,500 rpm tells
> me the mixture is really good but most likely the cat is shot. However,
> this appears to be idle only tests so do not worry too much yet. A new cat
> will clean it up but it will not last long. You should really be able to
> get the pre-cat HC at idle well under 150.
>
> The high HC at idle has all the tell tale signs of an idle miss. Check the
> ignition timing and set as per the Bentley. Follow the procedure of warm
> engine, disconnect the temp 2 sensor while it is running and then set the
> timing. After reconnecting the sensor, set the idle speed slightly high to
> 950 or so. This does help. Make sure the oil is not overfilled and also
> that it is the correct viscosity. A compression/leak down test may be in
> order here. After confirming compression if you still have the miss and
> fail inspection again the next step is to check the injectors. Oh, first
> make sure there are no vacuum leaks. Small ones at the injector seals,
> manifold boots, etc, can be really bad. If you had an ignition miss fire
> you would also see the high HC at speed.
>
> With a good cat you should really see readings of near "0" for HC and CO.
>
> Dennis
>
> -----Original Message-----
> From: John Goubeaux [mailto:john@ucsb.edu]
> Sent: Thursday, February 07, 2008 9:28 PM
> To: Dennis Haynes
> Cc: vanagon@GERRY.VANAGON.COM
> Subject: Re: SMOG TEST failure
>
> Thanks Dennis,
>
> Good summary. Here are all the numbers in order to better diagnose:
>
> rpm              %CO2              %O2              HC(ppm)          CO
> %               RESULTS
>                      MEAS             MEAS             MEAS
> MEAS
> ______________________________________________________________________
>
> 915               11.9                  3.2                  424
>       0.55               GROSS POLLUTER
>
> 2571               13.9                 0.5                  66
>         0.55                  PASS
>
>
> Dennis Haynes wrote:
>
>> Emissions issues really are straight forward for those who know how the
>> system works, what should happen normally, and what causes the various
>>
> gas
>
>> failures. Results like you are the justification for emissions test
>> procedures and with your numbers you are definitely in the league of a
>> gross polluter.
>>
>> For starters, in order for anyone to diagnose you problem, you also need
>> to state the CO amount. For diagnosing, you really want to measure the
>>
> CO
>
>> before the catalyst. That is why there is a test port.
>>
>> I'll go over the gasses again and if someone wants, feel free to post
>>
> this
>
>> on the Wiki.
>>
>> Carbon Monoxide is the result of incomplete combustion due to
>>
> insufficient
>
>> oxygen being available or combining with the fuel to complete the burn.
>> Yes, this is the one that is mixture, and temperature related. Why
>> temperature? The big un-vaporized fuel molecules may not get the oxygen
>> even if it is available. That is why there are winter fuel blends and we
>> need enrichment to get cold engines started. If the CO is in limits, the
>> fuel injection is basically working. The Vanagon should be able to get
>> near 1% even before the Cat.
>>
>> Excessive Hydrocarbons. This is fuel that never started to burn or get
>> ignited. Yep, raw gas out the pipe. Usual causes are ignition miss fire,
>> leaking valves, rings, etc. Another phenomenon here is what is known as
>> the "Lean" miss fire. This is due to slight differences in mixture
>>
> amongst
>
>> cylinders with the leaner one failing to "light up". This is that crazy
>> intermittent miss that can drive you crazy. The Vanagon engne is really
>> prone to this due to the poorly designed intake system. Over advanced
>> ignition timing will also add to this as the advance timing will require
>> much less air and fuel to maintain a low idle speed. This results in
>>
> poor
>
>> swirl and mixing and the fuel mix will fail to light. If an oil change
>> fixes this, consider you have a ring or valve-guide problem. Excessively
>> lean or rich mixtures will result in the miss fire.
>>
>> Oxides of Nitrogen (NOx). This is the result of excessive flame
>> temperatures. Engine design, ignition timing, and load all add to create
>> this. The controls are timing settings (why we have the dual diaphragm
>> distributors before Digifant), low compression, most vehicles EGR, and
>>
> in
>
>> everything 81 and later the three way oxidation reduction catalyst with
>> the O2 sensor for final mixture control. The downside of this is that we
>> can no longer use lean mixtures to improve fuel economy. This is also a
>> major problem with Diesel engines as they have high compression, and
>>
> lots
>
>> of excess air.
>>
>> Now give us the rest of the readings and I will try to give you
>>
> diagnoses
>
>> and direction. Resist the temptation to tamper with the afm and make
>>
> blind
>
>> adjustments or start changing parts.
>>
>> Dennis
>>
>> -----Original Message-----
>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
>>
> Of
>
>> John Goubeaux
>> Sent: Thursday, February 07, 2008 5:31 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: SMOG TEST failure
>>
>> My 90 failed the California smog test today. In short, the idle values
>> were off with HC ppm at 424 where max allowed is 120  though the 2500rpm
>> values passed fine and are way below limits.
>>
>> So I am looking for some clues on where to start with this, and while I
>> realize it might not be straight fwd, thought I would see if anyone has
>> some insights. Replacing components one by one might get expensive so i
>> was hoping on narrowing it down on what it **could be.
>>
>> Idle is fine though it has been rough for a while at startup and I have
>> had intermittent, what appears like missing at high speeds when
>> accelerating.  I had thought that i was seeing what folks refer to as
>> the "vanagon syndrome"  but with with the idle values like these am
>> thinking that it could be as a result of  the idle control valve (though
>> it vibrates), the idle control unit or the coolant temp sensor (which i
>> am told can cause a rich mixture.
>>
>> It looks like Bentley has clear steps to trbl shoot the idle though I am
>> not sure, without the proper tools, if I can make the needed adjustments
>> it calls for.
>>
>> Thanks in advance for any wisdom that can be shared..!!
>>
>> -john
>>
>>
>>
>
>
>