Don

idle stabilization valve on the top of the valve cover that normally hums
could be sticking.  also look for air leaks and check the wiring to the
hall sensor.  supposedly some people have had ecu's fail on digifant II
but i have never seen one go bad.  temp II and O2 are easily checked via
the normal bentley proceedure with a multi-meter.  actually the whole
digifant system only needs a multimeter for trouble shooting and that is
the beauty of it.

jonathan

On Mon, 11 Jun 2007, Don Hanson wrote:

>  Suddenly my Digifant FI VW motor started misbehaving on start-up.
Where do I start looking tomorrow AM?  Temp II sender?  O2 sensor?  Both
were recently replaced...within a year anyhow..Recent fuel pump and
filter replacement, also.
>
>  Ok, a bit more info.  This motor isn't a water boxer, but all the stuff is almost identical.  It's a 92 Rabbit/Cabriolet 1.8 liter inline 4 with vigilant injection.  Vanagon fuel system, Vanagon intake..
>   The engine starts as normal, then goes hunting around the lower rpm range without me touching the gas.  Does this for about a minute, then settles out and runs perfectly normal until the next time it is started cool...I think...(this all just started this afternoon.)  .that when warm, the missing and hunting won't happen.  If I give it gas, it stumbles badly during these starting up episodes.
>
> Until this recent change in  behavior, the motor would start very well with no throttle and idle at an increased rpm until it warmed..about maybe a minute..then it would drop right off to it's regular steady smooth idle....Now, it hunts around, maybe drops a cylinder or two for a few seconds, comes back to high rpm, then sputters a bit...until about a minute passes and it gets right again and  idles smooth and regular, runs down the road perfectly..
>
> Something in the fuel system for almost sure..Loose or shorting wire to one of the sensors is my bet, but anyone want to guess or point to the one it may be?
>  Thanks, I will report back if and when I find the problem..
>
>  Don Hanson
>
>
>