Date: Thu, 8 Jul 2004 15:52:44 -0500
Reply-To: Larry Alofs <lalofs@RCN.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Larry Alofs <lalofs@RCN.COM>
Subject: Re: fuel/air mixture diagnostics
Content-Type: text/plain; charset=us-ascii; format=flowed
This is a definite possibility. It has happened to me. My 91 GL blew
out a gasket at the Y connector while I was driving back from Atlanta to
Chicago recently. On that part of the trip I got 16 and 17 mpg rather
than the usual 19. After fixing the leak, the mileage went back up.
The vanagon exhaust is unusual in having so many joints and gaskets
upstream of the O2 sensor and some leaks can draw air in and fool the
system. You should be able to feel or hear any significant leak. When
the engine is cold, start it and get under there quickly before things
get unpleasantly hot. Move your hand around all the joints to feel for
leaks.
Don't worry about reusing old gaskets IF they are in good shape.
BTW a steady low voltage from the O2 sensor , indicating a lean mixture,
might also result from a sensor that is fouled by soot. Some have said
that these sensors can be cleaned by heating with a propane torch. YMMV
good luck,
Larry A.
Craig Oda wrote:
> I was thinking. If there is a leak in my exhaust system, then is it
> possible that air is leaking into the exhaust system and fooling the
> oxygen sensor into thinking that it is lean, when in reality the
> mixture is rich?
>
> I may have reused the exhaust gaskets when I took apart my exhaust
> system the last time.
>
> It's not so fun to mess with the exhaust pipes, so if this isn't a
> real possibility, I would rather not mess with it.
>
> The inside of the exhaust pipe does look black and sooty.
>
> Any other ideas?
>
> Regards,
> Craig
>
> On Thu, 8 Jul 2004 09:03:25 -0700, Craig Oda <craigoda@gmail.com> wrote:
>
>>I have some problems getting my automatic transmission van to
>>consistently idle when stopped at a light, especially if the idle is
>>set at 900rpm. I need to set it higher.
>>
>>I have a voltmeter attached to my oxygen sensor and it is indicating a
>>very lean mixture. I have the air-fuel screw on the AFM almost all
>>the way in (clockwise). When I get home tonight I'm going to try and
>>move the ratchet wheel inside the AFM that controls spring tension.
>>Then, adjust the air-fuel mixture screw again.
>>
>>I'm new to these diagnostics. For a while, I assumed that my van was
>>running rich because there is black soot on the tip of the exhaust
>>pipe. Does black soot on the exhaust indicate a rich or lean engine?
>>Or, is it possible that the soot could be an indication of either
>>condition? It seems to me that I can smell unburnt gas from the
>>exhaust. However, this could just be my imagination?
>>
>>The O2 sensor reading indicates the engine is lean. The soot makes me wonder.
>>
>>Before I fiddle with the AFM, I thought I would ask the friendly vanagon people.
>>
>>Other info:
>> - O2 sensor is less than 6 months old
>> - new fuel filter, air filter, fuel pump
>> - new spark plugs, plug wires, rotor, distributor cap
>>
>>Also, I have a vacuum guage from Sears that I never used. I may tap
>>it into my vacuum hose system tonight for a test. Where Should I
>>connect it? I can't detect any vacuum leaks with ear or carb cleaner.
>>
>
>
| 
