[T3] On my 73 square

William Jahn willjahn975 at gmail.com
Sun Sep 15 15:14:08 PDT 2019

The trigger points are NOS Bosch I got in 2003 as are the injectors. I
first noticed this miss in 2009 by accident engine running taking things
out the the back I heard it yet didn't notice it driving the car. I just
let it be until when I decided to check the generator out put watching the
voltmeter and found it was really difficult to raise the RPM and hold it
steady just above the 1,000 RPM idle to about 2500 RPM it would hang and
raise and lower just unsteady. That's when by chance I unplugged TS1 and
found it cleared it all right up.

 I don't know what would go wrong with the ECU , I had to have it jumped
twice once by another car and once by a portable jump unit , it was not
like either had real high voltage and everything else in the ECU works fine
and the jumps were back in 2002 or 3 and I had the car running while
talking to people and it was all connected and ran steady well after that.

 I have no idea how the ECU works as far as the TS2 and TS1 internal
workings. I know they are on different connectors and both read a ground
reference one through the head and one through the ECU pin 13 I think. From
what I can tell pin 1 is the input for TS1 and 13 it's ground 11 is also a
ground and 14 seems to be the TPS ground since it had the EGR . I removed
the valve and the relay and had no issues running. Left 14 as it was. If
there is an issue in the ECU it would seem to be pin 1 and how the ECU
reads it. I've looked at block diagrams and from what i can tell TS1 and
TS2 are different paths.

 If I had a fuel pressure issue I have no problem at high speeds it never
lacks power . All the issues seem to stem from TS1 so first I need to check
pin 1 & 13 at the ECU connector to the plug on TS1 so I know I have a good
connection with no opens or short to ground on either wire. In an a way it
seems they are fine or unplugging TS1 would not affect anything unless pin
1 has an issue. I certainly hope it's not the ECU sounds like an expensive
replacement if I can even find one known to be good. I did find the testing
for the Bosch tester that plugs into the ECU and seems like it will tell if
it is the ECU. I just saw the one with the lights not the gauge.

On Sun, Sep 15, 2019 at 2:07 PM Jim Adney <jadney at vwtype3.org> wrote:

> Bob,
> Clearly I'm aware of the long history of this. The problem, as I see it,
> is that
> it's pretty clear that this is NOT a pressure sensor problem. That's
> because it
> happened suddely, and it happens with different pressure sensors. I'm here
> in the midwest with the very same car, '73 AT/FI, running the same FI
> system
> without his symptoms.
> To me, it makes no sense to mess with the pressure sensor unless we're
> pretty sure it's a pressure sensor problem.
> Or, as Gene Berg would put it, "Don't put a Band-Aid on your elbow for a
> scrape on your knee."
> I understand that there are people out there who jump at the chance to
> "adjust" the pressure sensor. Those same people would probably suggest
> adjusting the brain, too, if it also had a simple, one-knob, adjustment
> somewhere.
> People tend to look at problems like this as one dimensional problems: You
> either need more or less of something. Unfortunately, even carbs are not
> one dimensional, with their interplay of main jets, idle jets, emulsion
> tubes,
> and throttle pumps. FI is even more complicated.
> I have a friend who refers to things like this as, "wandering around in a
> multi-dimensional parameter space." That may seem complicated, but it
> really puts it in a nutshell. Which are you going to adjust, U, V, W, X,
> Y, or
> Z? Any one of them can make things richer, but each has different effects,
> under different loads, and at different speeds, and their effects all
> overlap.
> It's possible that he needs another brain to swap in, as it's always
> possible
> that something really has gone wrong in there. That's just about the only
> thing he hasn't tried. That's an unlikely failure, but anything's possible.
> I thought we had it fixed when he found the bad relay, but that didn't
> help. It's
> possible, however, that the fix on the relay didn't last for long. There's
> also
> the fuel pump relay, and he hasn't monitored the fuel pressure while
> driving.
> Then there are the trigger point contacts, although those should make for
> poor operation at speed as well as at idle, which he doesn't see. Still,
> I'd like
> to see those get adjusted, because it's a common problem and is something
> simple I can do here, but it's not a DIY project.
> There are so many trivial mistakes that can happen that will make things
> bad. Daniel mixed up #21 with #12 in the trigger point connector, which
> made some brains work and others not (how could that be?) That wasn't
> found until we put the Bosch tester on it. Someone else found 2 wires
> swapped on their pressure sensor connector. That kept the engine from
> running at all, but I'm amazed that he was able to find this at all. I've
> seen
> the head sensor wire connected to the ground lug on the pressure sensor,
> and that car still ran, but poorly.
> So, my recommendations: try a different 048 brain, monitor the fuel
> pressure
> and the voltage to the fuel pump while driving, monitor the output voltage
> from the power relay while driving. Also see if the problem goes away if
> the
> TPS is disconnected. Then get this car to a Bosch tester and someone who
> knows how to use it. A second set of eyes is often able to pick up a
> problem.
> Jim
> On 15 Sep 2019 at 19:30, bobsnotch at aol.com wrote:
> > That's the thing Jim, that "miss at idle" started him down this road of
> going thru everything.
> > He's had a couple of threads about this on the Samba, chasing it. So
> far, the big consensus
> > has been to adjust the MPS, so he can at least plug in the IAD sensor.
> > The miss has been bugging him since 2016 or maybe 2017, as he can't get
> rid of it. He
> > ended up unplugging the IAD TS to help a running issue back then, after
> he got the correct
> > MPS on the engine (had been running a "D" unit).
> > He originally blamed it on the 10% ethanol being added, but we know
> better. That's not it.
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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