Interesting ride to work
urq at pacbell.net
Thu Mar 15 23:56:19 EDT 2007
... when that happens you would not expect the tach to immediately drop to
zero as reported ...
On the urq/WX engine there are three sensors that can cause the loss of
spark that would cause the tach to drop immediately like that ... the Hall
Sender in the distributor, the engine speed and and engine reference sensors
which mount on the bellhousing and sense flywheel teeth and the reference
pin. My urq experience would make me lean toward the Hall Sender (either
broken or a change in cam timing) ... of course if the cam timing changed
you would not expect the immediate recovery upon restart. My experience on
the V8s is that the flywheel senders can and do fail ... and yes, they are
available new for $100-150 ... perhaps not the ones specific for the WX, but
ones that will work.
The other possibility is on the other end of the F/TCU ... that being the
ignition driver module has failed and you lose spark that way ...
Unfortunately it is going to be difficult to identify the flaky sensor as
there is no diagnostic capability on the WX/MAC-02. I've been tempted to
build a jumper block that can install in line to the connector to the ECU
which would allow you to monitor all of the I/O ... much like the box Audi
uses for diagnosing older ABS systems ...
San Jose, CA (USA)
> My 4000 once quit like this. Bad Fuel Pump Relay.
> LL - NY
> On 3/15/07, DGraber460 at aol.com <DGraber460 at aol.com> wrote:
>> This AM, I am jaunting on to work with the usual Audi flare when at ~60
>> steady speed that old URQ went spark dead. Tach dropped to zero. No
>> bumps, etc. I coast to the side of the road in gear all the while
>> everything I can think of (including the ignition switch) to no avail.
>> All the
>> other electrics worked fine but the tach didn't even bounce.
>> Once stopped, I offer a heavy sigh of "What Now?!", and turn off the
>> ignition. Figuring I had nothing to lose, I turn it back on and crank it
>> and it
>> fires right up and ran fine the rest of the day.
>> My first guess is the TDC flywheel sensor. Is there anything else that
>> totally cut spark this way?
>> Maybe I have a Microsoft programmed ECU, and just wants to be "rebooted"
>> once in a while.
>> My other URQ did something similar about once every 9 months, but
>> would buck
>> and backfire and finally completely die. It would also start right up
>> the "reboot". Not sure but I might be using the same TDC sensor from
>> that car.
>> Are these sensors still available new? If so from where? The used spares
>> have are all a bit dodgy.
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