[T3] Surging and lurching! Fastback with FI

jaredkohler at gmail.com jaredkohler at gmail.com
Mon Aug 28 10:18:57 PDT 2017


Jim,

First; engine was idled good. Issue only happened upon acceleration.

Started to investigate Sunday morning...

Checked fuel pressure (hadn't done this in a long while so why not?) it's
at 28, which I know is on the low side of the scale, per Bentley Book.
Issue?

My TVS wasn't the problem just as you suspected. I pulled the cover,
inspected, blew out some dust and dirt, and went back through the
adjustment directions (Bentley) listening for the 'clicks'. Then locked it
back down. It was a little off adjustment.

I then went back through ALL of my electrical connections reseating every
plug and connector. Then moved onto the vacuum hoses. Good and tight.

After ALL this, it seemed to start a bit better and idle slightly smoother.

Then, just out of curiosity, I looked at my ignition points. Very small
burn mark which wasn't allowing my feeler gauge to pass through. Hhmmmm?
Luckily, in my home parts dept. I had a new set of points. So, installed
those and gapped to .018.

Then I got a tad more eager and decided to check the plugs. Perhaps one or
all were fowled? Maybe? Hhhmmm? One plug's gap was way under and the other
were a bit on the black side. After cleaning and setting gaps to .024 I
reinstalled the plugs.

Now, the engine was looking real nice. Everything in it's place and cleaned
up. Test drive time. Wow, the problem was gone! Back to normal performance
upon acceleration! I'm thinking reseating the electrical connections and
installing the new points set was the fix! All in all, the old Fasty needed
a refresher.

I was happy and excited. Keeping with my momentum, I decided to lube the
front end. All zerks were thirsty! Then I moved on to installing a fresh
fuel filter and checked my fuel line connections up front! All looking good.

Wow, what a Sunday!

Thanks as always to EVERYONE!

Jared

Goleta, CA

On Sat, Aug 26, 2017 at 2:01 PM, Jim Adney <jadney at vwtype3.org> wrote:

> On 26 Aug 2017 at 12:34, jaredkohler at gmail.com wrote:
>
> > Now, out of the blue, the throttle / engine response upon take off surges
> > and lurches violently.
>
> Is the idle normal when this happens?
>
> > I pulled the cover to my TVS (Throttle Valve Switch) to check the
> contacts
> > and all looks as it should. Clean and making contact. I never changed
> it's
> > position to begin with though. The FI TVS harness plug (4 wire) was also
> > connected tightly.
>
> I have a faq on adjusting the TVS, but it's almost never the problem. The
> quick check is to simply unplug the TVS and see if the problem goes away.
> If
> it does, readjustment, cleaning, or replacment may be called for. (Note: I
> have never had to replace one of the '70-1 4-terminal TVSs.)
>
> > My next step will be to check the fuel presser using my fuel pressure
> gauge.
>
> Probably not the problem. The fuel pressure very seldom changes. It's a set
> and forget item. On your '70, the pressure should be ~30 psi.
>
> Check anything that might be loose in your drive train: lug bolts, CV joint
> bolts, etc. Anything that might add to backlash in the drive train can
> lead to
> bucking problems. Could be a worn CV joint or broken springs in the clutch
> plate.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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