Date: Thu, 7 Feb 2008 21:52:41 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: SMOG TEST failure
In-Reply-To: <47ABBE3B.7020404@ucsb.edu>
Content-Type: text/plain; charset="iso-8859-1"
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
>
>
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