Date: Fri, 25 Oct 2002 13:06:19 -0400
Reply-To: Laurence Smith <laurence@ALANASMITH.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Laurence Smith <laurence@ALANASMITH.COM>
Subject: Re: '89 2.1i digifant cutting out. Really need some help on this
one... ; NOT SOLVED!
In-Reply-To: <171105540D7EE44FA177B599FEBA98F7EA4643@ta-exch.monitrax.com>
Content-Type: text/plain; charset="iso-8859-1"
First assumption is that the ignition wires, spark plugs, distributor
cap and rotor are all fine.
I like to think iof probabilities given the symptoms. So here goes:
If the stumbling hgappens when cold then you can rule out the O2
sensor. It only influences the ECU when warmed up (which is about 1
minute). When warm and water (from rain) gets on the O2 sensor or its
wiring can cause sometimes stumbling. Low probability.
A dying ECU is rare. Low probability.
The Temp II sender doesn't react fast enough to cause drammatic
stumbling. Low probability.
Injectors are awful reliable. Low probability of a problem here. But
they do ground on the firewall (via the ECU) and if this ground is
getting bad through corrosion you would get intermmittent bad
grounding especially as the weather gets colder and metal shrinks a
bit. This would cause stumbling. Medium probability.
If there was gas starvation, but the stumbling only lasts a second,
then I would omit gas starvation as the culprit. Why? Because if
there is a blockage of some sort, then the stumbing would vary from a
second, 5 seconds, occassional stalling. You imply that the the
stumbling time is quite consistent. Also, I think of fuel pumps as
either working or not. Medium probability.
The throttle switch is only a factor when idling or under "pedal to
the metal" load. So this may be ommitted. Low probability.
The idle stabilizer and control unit may be flakey, but I think this a
low probability.
If the stumbing went away for a while (days or weeks) then I would
omit problems with the AFM. Also, it is not the Vanagon syndrome
because the problem also happens when cold. Medium probability.
The hall sender can go flakey and send intermittent reading to the ECU
which would in turn cause stumbling. I think it is a low probablity
however.
The fuel pressure regulator tends to either work or it doesn't. They
are usually reliable. Low probability.
The coil is a good candidate for investigation. If it is starting to
die it will provide unreliable sparks. I would check this out. High
probability.
You may have a vacuum leak which may starve the engine of fuel and
cause stumbling. If your idle is going up and own this may be
something to investigate. Check the rubber connector connection
between the air filter/afm and the throttle body. Medium probability.
Ignition key/lock electrical portion can be flakey and cause
intermittent power signals especcially when pulling away from a stop.
Low probability.
That's all I can think of at the moment. Good luck!
Laurence Smith
Hamilton, ON
90 Westy (fanumbos)
> -----Original Message-----
> From: Vanagon Mailing List
> [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> Of Jamie Bowen
> Sent: Friday, October 25, 2002 5:59 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: '89 2.1i digifant cutting out. Really need some
> help on this
> one... ; NOT SOLVED!
>
>
> Still got this damn problem. I thought I had fixed it but
> its back with a vengence.
>
> I get an intermittant cut out when driving that lasts for
> around a second and then the engine recovers. If it had
> enough revs to carry it through the second that is. If I'm
> pulling away it will cut. I happens under no particular
> conditions, when the engine is hot or cold, at speed an
> when going slow. It seems to happen more under load, but I
> think that I am just noticing it more then.... I seems
> pretty random anyway.
>
> Last night I drove with a timing strobe attached to
> cylinder no 1 and observed that there is still a spark when
> the van cuts out. This must mean that there is fuel
> starvation right? I guess that fuel starvation could come
> from either blocked fuel lines/filter or bad pump, or from
> the ECU telling the injectors not to inject. I replaced the
> fuel filter after the test, but to no avail. The fuel pump
> is obviously working some of the time. Could it be a bad
> fuel pump relay?
>
> What signals does the ECU use to determine how much fuel to
> squirt? I'm guessing that it uses engine temp (temp II
> sensor), RPM (from the coil?) and engine load (from the
> AFM). Am I on the right track here? Is there anything else?
> Presumably on a digifant the O2 sensor is also used....
>
> Any suggestions will be greatfully recieved!
>
> Jamie.
>
> I'm going to be SO happy when I get this fixed......
>
