[T3] Problem starting / warming up

[Dave Hall]

Most likely Jim has the answer, but have a look in the distributor and check
that the wire from the points isn't broken.  I had this happen in a Beetle
and the revs rose than cut out until slowing, and then rose again.  It
seemed possessed, revving and dropping back all on its own!  It turned out
to be a broken baseplate ground wire which was making contact when the
distributor baseplate was in its rest position, then breaking contact as the
distributor advance kicked in.  I can't believe it's ever happened to anyone
else, but I know it is just possible, having experienced it!

Dave
UK VW Type 3&4 Club
===================

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: 27 September 2012 06:21
To: type3 at vwtype3.org
Subject: Re: [T3] Problem starting / warming up

On 26 Sep 2012 at 18:40, Joshua MacDonald wrote:

> My '70 fastback has recently begun behaving as follows (in Mountain View,
CA):
> 
> It turns over and fires up, revs to idle speed, then abruptly stops 
> firing, the engine speed free-falls by maybe 25%, then it starts 
> firing again. The process repeats for several minutes--idling up, free 
> falling down, ...

This sounds like what typically happens if the idle is set too high. 
The FI is programmed to automatically turn off the injectors if the RPM
rises above something like 1400 and stay off until it falls back below
something like 1100. 

> The engine sounds normal on the upswing. The free-fall sounds just 
> like it does after cutting-off the ignition.
> If I depress the accelerator, the engine revs faster but free falls 
> just the same.
> After a couple of minutes, depressing the accelerator will rev to a 
> higher RPM than at initial start-up, but still the same free-fall.

If the throttle valve switch (TVS) is adjusted properly, this behavior
should stop as soon as the throttle is off idle. Try unplugging the TVS:
this will make the FI think you're no longer at idle. If this stops the
behavior, then everything is normal except that your idle speed has been set
too high and the TVS is either broken or misadjusted. (most likely the
latter.)

> Eventually, it resolves, I assume because the engine has warmed up.
> During the idle-up/free-fall cycle, I possibly hear the sound of a 
> relay switching on/off under the dash. It's also possible the the 
> battery voltage is a bit low.

While it's doing this, is it possible to get it out on the road and driving?
If so, your answer is above. If not, you have a larger problem.

If the relay under the dash is actually switching on and off, this is a
different problem. For that, the first thing I'd check would be to make sure
that the screw holding the relay under the back seat is tight.

Check your battery voltage at medium rpm after a good drive to warm
everything up. It should be 14.1 - 14.4 V, measured across the battery. It
will be 1/2 V higher at the generator and 1/2 V lower if you measure at the
fuse box.

If it's below 13.5 V at the battery, replace the voltage regulator.

 If it is below
--
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************

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