Date:         Fri, 24 Jul 2009 13:09:57 -0300
Reply-To:     Dave Arthur <dave.arthur@NSCC.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dave Arthur <dave.arthur@NSCC.CA>
Subject:      Re: No Oil filler cap=poor idle..observation on Digifant..
Comments: To: Don Hanson <dhanson928@GMAIL.COM>
In-Reply-To:  <6bc66ccf0907240850j5595b8b2h6fdc2f6c637c6e2d@mail.gmail.com>
Content-type: text/plain; charset="US-ASCII"

On A WBX, and certainly your engine also... There is a hose, positioned
between the AFM and the throttle body, which connects to the oil breather
tower. This hose purges the crankcase. By leaving the oil filler cap off an
abnormal amount of air can enter the throttle body without being metered by
the AFM, to my mind this should cause a lean condition, but I'm not sure.
Certainly it will cause a problem.

Best Regards

D


On 24/07/09 12:50 PM, "Don Hanson" <dhanson928@GMAIL.COM> wrote:

>   My van has an inline four VW motor..Digifant II injection, lots of the
> same parts as a WBX.  So yesterday I was changing the oil (to 20-50 dino)
> without changing the filter...I do that every second change..3000 mi (+/-)
> intervals.  I was distracted during my refilling and somehow I spaced-out
> replacing the cap on the filler.  Started it up and had a really poor
> idle...very similar to what was going on just before I replaced my Idle
> control valve (about 4000mi ago)  I was puzzeled, thinking "Jeeze, feels
> like some connector has come loose"..but I wasn't even inside the engine
> compartment and it happened suddenly without any hints before the oil
> change.  Then, standing behind the van scratching my head, I noticed my
> licence plate a bit askew and found my oil filler cap wedged in there rather
> than on the filler pipe.  Put it back on and re-started...in about 10
> seconds, the idele returned to normal...
>
>   So, there must be some kind of vacuum supply that's dependent on a sealed
> sump, right?  Anyone want to try to explain why leaving the oil filler cap
> off might cause the engine idle to go all wierd...kinda felt full rich..
> though it was so windy in my Gorge driveway that I couldn't see any dark
> exhaust or smell anything..
>
>   Don Hanson