[T3] Intermittently running on two cylinders

[Jacob Adam Schroeder]

Thanks Jim.  We have had family in town this week and I was unable to get
to the car today, but I appreciate all the input.  I found the grounds (as
suggested) to be on the center of the crankcase, consistent with mine being
a 1972 (I'm glad to know I at least hooked those up right 15 years ago when
I rebuilt the engine).

The problem occurs (when it does) at idle on a cold engine.  Although, just
because the engine is cold does not mean I'll have the issue, but when it
does happen, it is on a cold engine at idle.  Revving the engine up (no
matter how high) will not remedy the problem.  It just revs up the 2
cylinders.  You are correct with there being NO power when this happens.

Also, the problem always happens on the same two cylinders and, oddly
enough, when it happens to one it happens to both.  Thus, I never have had
the situation (that I know about) where it is running on three cylinders.
It is always 4 or 2.  I will try investigating the things you have
suggested and report back.  This week at work is looking busy, so I may not
get to it until next weekend.  Stay tuned . . .



On Sat, Dec 1, 2012 at 1:49 PM, Jim Adney <jadney at vwtype3.org> wrote:

> On 1 Dec 2012 at 11:46, Jacob Adam Schroeder wrote:
>
> > My car has developed an issue lately where occasionally it will feel like
> > it is running on two cylinders.  When it does this, I can pull the wires
> > from the fuel injectors on cylinders 2 and 4 and notice no difference in
> > the sound of the engine.  If I pull 1 or 3, I hear the RPM decrease and
> it
> > sounds like it is running on only 1 (if that is even possible).  It is a
> > 1972 Squareback with stock FI (except for Pertronix electronic ignition
> --
> > which I plan to return to the stock set up soon).
>
> Is this all the time, or just at idle. Sometimes we can get confused
> by something that happens only at idle. It's not uncommon to have a
> cylinder or 2 not fire normally, at idle with a cold engine. If this
> is happening while driving, you would feel like you had almost NO
> power.
>
> It's not the Pertronix, because that would effect any or all
> cylinders. It's probably also not the same ground problem as
> Daniel's, because 68-9 injector grounds are different, and have their
> own very special problems.
>
> Certainly you can go around randomly cleaning up every connector in
> sight, but you're actually more likely to do harm than good by this
> approach. Likewise with fuses, of which NONE serve the FI
> electronics.
>
> Cylinders 2 & 4 don't point to any particular problem. If it's always
> those 2, then there must be a problem with those cylinders. It could
> be FI or it could be ignition, but IT MUST BE SOMETHING THAT'S NOT
> SHARED IN COMMON WITH 1 & 3.
>
> The first thing I would check would be the resistances of the spark
> plug connectors on 2 & 4. They should measure ~1000 Ohms. If they
> measure infinity, you've found your problem. Replace the bakelite
> ends and you're back in business.
>
> Also check the inside of your distributor cap and wipe off any
> condensation you find in there.
>
> If that doesn't do it, the next thing to check would be the tightness
> of the female connectors onto the injector pins. To do this you have
> to take the connectors apart. This takes patience and possibly a
> special tool, for which a Bobby pin might work. You have to back the
> 2 pins out of the white plastic connector body and then check each
> one to make sure it fits snugly onto the injector pins. If they are
> loose, you can squeeze them VERY gently with pliers and tighten them
> up. Be careful, don't get carried away, or you'll end up making extra
> work for yourself.
>
> If you find any of these to be loose, you're probably better off
> working your way thru all 4 injector connectors. Yes, even the ones
> that seem to be working okay most of the time. This is a fairly
> common problem, because Bosch seems to have made replacement
> injectors with slightly thinner pins starting around ?1980? Fixing
> these connectors is quite a bit of fiddly work, but it's often very
> rewarding.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
> _______________________________________________
> VWType3.Org mailing list - type3 at vwtype3.org
> http://lists.vwtype3.org/listinfo.cgi/type3-vwtype3.org
> Contact gregm at vwtype3.org if you need help with the list.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.vwtype3.org/private.cgi/type3-vwtype3.org/attachments/20121202/1e911ed6/attachment.htm>