84 4KQ Cutting out

[Chris Hall]

As anyone who reads the email on this list knows, I've suffered from
this in 3 different ways, and I'm finally happy to say that I've fixed
the problem 3 different ways as well.

>From my experience, If the tach drops like a rock, then it's almost
certainly the Ignition Control Module.  Don't believe the "this hardly
ever fails" stuff you might read online... happens all the time.  Try
to get one from a junkyard.  I think many different cars share the ICM
in our cars, so do a little part number research online and try to get
one cheap out of one of those cars... because a good Bosch unit is
around $100.  My 83 CGT had a Fairchild unit in it, I believe my 85
had a bosch, and I bought a brand new Lucas module for $5 on ebay
which I burned up before realizing the coil was killing them all.

If the tach glides down to 0, suspect the Hall Effect sender under the
distributor cap.  Again, don't believe the "these hardly ever go bad"
comments all over the internet.  Up until re-testing, I thought
disconnecting the Hall Sender as the engine runs made the tach fall
like a rock as well.  Nope.. it glides down to 0.  Same goes for the
Fuel Pump Relay... tach glides down to 0.

If you do replace your Ignition Control Module and the car runs fine
for a while then starts acting up again, your coil is probably out of
spec and drawing too much current through the ICM, and burning it up. 
So, test the coil's ohms to the specs you find in the repair manual. 
Unfortunatly for me, the specs listed as the 5 cylinder specs are
wrong in all the manuals, they are for the 4 cylinder models.  84
quattro is a 4 cylinder anyway, isn't it?  Guess you're safe there... 
I replaced the ICM in my car 2 times before I read a solitary post in
some archives somewhere that said the coil can destroy them and that
the specs in the books were wrong.  Replaced the coil and the ICM, and
the car was fine.



Recently, I was having the stalling problem again, and since I have a
new coil and ICM, and couldn't prove anything else was causing the
problem, I replaced the Hall Sender because it's one of the few things
that can have this type of stalling effect on the car AND I figured
it's better to be running around in a 20 year old car with a NON-20
year old hall sender that can cause the car to stall.  I couldn't even
get the engine to stall by shaking the connector for the Hall sender
like people suggest, but I decided that maybe the sensor inside maybe
have been damaged from being heat soaked over 20 years, just like the
coil most likely had.

I replaced it about 3 weeks ago, and the car's been fine since.

Thinking back to all recent times where the car stalled, I seem to
remember it stalling when  a change in engine speed (and VACUUM) had
been happening... putting the clutch in and coasting to a traffic
light, flooring the engine, etc.  I now think that the wires (although
they LOOK fine) inside the Hall Sender have tiny breaks in them,
because what I DIDN'T know was that the Hall Sender in my car rotates
when the Vacuum Advance arm pulls it.  When it's rotated, the slack in
the 3 tiny wires allows them to move, and I'm sure 20 years of those
wires moving back and forth like that broke the copper wire.

Everyone on here suggested that I do more "testing" and not buy a $85
Hall Sender if I didn't "need" to, but like I said... that $85 (even
if it hadn't been the problem) at least insures that the Hall sender
in my car will be one less thing that's potentially going to leave me
stranded on the side of the road for "the next 20 years".

Other things to look at would be the throttle position switches, the
wires to and from the coil, the wiring to the ECU's temp sensor, etc. 
The ECU loves to shut the ignition off when it doesn't get a report
from one of the many things that send it info.

--
 
Chris Hall
badcomrade at gmail.com
"making girls cry since 1974"