[V8] 93 Audi V8 / AT ZF4HP24A

[Ingo Rautenberg]

You have to be pretty careful when making said diagnosis. I had almost
identical symptoms, except worse (with the culprit being the ignition
reference sensor).  When these sensors go, it triggers the ecu to cut the
power to the fuel pump relays -- yes, the  '93 (and I'm pretty sure the '92)
have two fuel pump relays. So I guess that's the third culprit behind the
engine timing and reference sensors.  Hey, whatever fixes the problem, I
say!

Regards,

Ingo

On Sat, Jul 11, 2009 at 5:26 PM, Dave Saad <dsaad at icehouse.net> wrote:

> First, one possibly significant detail: the speedo sensor is an
> electronic "Hall" device. It senses the presence of a magnetic field
> of a magnet that rotates past it.
> This is different from the RPM and Crank Position sensors which are
> simply coils of many turns of fine wire. They induce a voltage when a
> piece of iron passes by.
> So the Hall switch is an electronic switch with a 5-volt square wave
> output, and the others are analog voltage output that must be
> conditioned and converted to a digital signal.
> The hall switch has 3 wires - 5v supply (from the ECU), output
> signal, and ground.  If the sensor is known to be good, then the only
> other logical choice I see is that the 5-volt supply is crapping out.
> That seems to jibe with the other symptoms too.   That also means the
> ECU is the most likely culprit.
>
> Dave
>
>
> On Jul 10, 2009, at 10:55 AM, D Morralee wrote:
>
> >
> >
> > 93 V8 4.2 AT
> >
> > I've been having this intermittent problem for a couple of years .
> > It's one of those problems I've never seen any reference to .
> >
> > Here is the problem .
> >
> > Car runs great for the first 20 mins and then the speedometer
> > sputters back and forth to what ever speed you are doing 0 - 60 mph
> > ( car is now at operating temperature ). A couple minuets after
> > that the speedometer drops to O and just stays there . The Speedo
> > then stars to sputter up and down again but there is a difference
> > …. the engine then turns on and off like you were turning the ign
> > on and off ? This all happens very quickly not enough for you to
> > pull the car onto the side of the road . If you're in Stop and Go
> > traffic then sometimes you will have to restarted the engine . This
> > funky stuff only happens for a couple of mins and then the car runs
> > great. What is it ? I hope you're not reading this and thinking you
> > have the answer …. It's the Speedo transmitter ( G68 ) that is
> > causing the problem . The Speedo transmitter is on the ZF4HP24A
> > Auto Trans by the mulit switch . This sensor picks up the rotation
> > of the LH driveshaft and sends the signal to TCU & or the
> > speedometer . These sensors are build/designed like the ref / rpm /
> > abs sensors running on other parts of the engine and chassis . As
> > we are all aware that these sensors get heat cycled and eventually
> > die a slow death. Not sure how this all ties into the end result of
> > the car cutting out, but I do know that it is related to Heat .
> >
> > Other than that the new tires and rim combination has worked out
> > great . Tonight I'm picking up my and installing my new K&N filter.
> > Next week I'm getting some exhaust modification done . One of the
> > mufflers is coming off and new stainless steel pipes will be added .
> >
> > Well that’s my news . Superdave .
> >
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