84 4KQ Cutting out

[Chris Hall]

Huw wrote: 

> So, what are the "wrong" coil resistance specs in the Bentley and what
> are the "right" ones for the 5 cyl engine?  Thanks...


Greg Roa is the one that pointed out to me that the coil specs listed
for the 5 cylinder engine coil in the Bentley / Hayes manuals were
actually for the 4 cylinder engines.

Here is his post at Audifans.com that turned me on to why my ICMs kept
burning up, followed by what he had to say in 3 private emails I
shared with him ( i removed my text from the emails to clean them up):

In http://www.audifans.com/pipermail/quattro/2001-July/030649.html
Greg Roa said:

"Hello all,
I finally think I may have found the answer to why my car kept burning up
igniton modules.  Went to figure out the problem this evening, and checked
the values of the coil against what bentley shows.  Everything appeared in
spec.  I was getting 3200 ohms of resistance from terminal 4 (center pin, to
dist) to terminal 1, and .8 ohms between terminal 1 and 15 (pos and neg coil
terminals).  This matched up with the ranges that I was supposed to be
getting.
Upon closer inspection though, I noticed that the coil shown in the Bentley
was different than the one that I have in the car.  I had been using the
diagnostics for the 4cyl cis-e, as most of the tests are the same as for my
4kq, and bentley does not have any info for 5cyl cis-e cars.  Looking at the
specs for the cis-eIII cars, I noticed that it uses the same coil, and the
specified range between terminals 1 and 4 is 4000-5000 ohms.  So, my coil
had too low of resistance, and was shorting out the ignition module.  Yup,
I'm an idiot. 
Dropped the new coil in, and new replacement module, and car seems to be
running quite well.
So, I will test it over the next few days, and see how things go.  Thanks to
everyone, and thanks a bunch to Paul Cole.  He has been helping me out a ton
on this problem, and is a great guy, even if he is an electrical engineer.
; ) 
So anyhow, thanks to everyone on the list.  My car's ignition module thanks
you too.
 
Greg Roa
Cincinnati, OH
86' 4kcsq
93' 90 CS
83' 944"

========================

EMAIL 1

That (audifans.com) post has the correct values in it.  You say that
your 85's coil is testing out at 2400-3500, so it sounds very similar
to what mine was reading.  I'm not 100% sure that the coil was the
same between 85 and 86, but I don't see any reason why it wouldn't be.

Hope that helps you out!
Greg Roa

=========================

EMAIL 2

 I was working for a while with an electrical engineer on the list. 
He went through all of the wiring diagrams for me to figure out what
it could be.  The only thing that he could find that could cause the
symptoms was the coil.  The reasoning was, if the coil is drawing too
much current through the ICM because the resistance was too low, then
the ICM would overheat after a while, and malfunction.

One other thing that I would make sure of, is that you have the
dielectric paste, or whatever in between the ICM and the aluminum
mounting plate.  The mounting plate acts as a heatsink, and the grease
helps to transfer the heat to it.

Good Luck, and let me know how it turns out!
Greg Roa

========================

EMAIL 3

I found the specs in the bentley manual under the CIS-3 information. 
It's very confusing the way it's laid out.  The CIS measurements
(right fuel system) are for the 4 cyl coil.  The coil is different
than the 5cyl coil.  I read though it very carefully, and figured it
out using the pictures, and other cryptic clues.  I spent a _lot_ of
time trying to figure this out.

Couple more things I would do.  Make sure your cap, rotor and wires
are all in good shape (clean up the contacts in the cap if they're
burned looking -or replace it, your call).  Also, I'd strap down the
connector for the hall sender -the connector on the side of the
distributor.  Most of the time the mounting piece that holds them to
the distributor gets broken.  The wires that lead from the hall sender
to that bracket get partially broken due to the flexing.  If they get
bumped around and the car looses signal from the hall sender for a few
seconds, it can do the same thing as you're seeing.  I've used a wire
tie on mine to keep it from bouncing around.  It may be that you had
two separate problems, that being the second one.

I went through three ignition control modules trying to figure out
what was going on with my car.  Don't feel too bad.  The good part is,
they're pretty easy to get from parts cars.  They're not a really hot
commodity.  I got offers for two or three of them from listers for
under $10.  I think one of them was free just for shipping.

If everything ends up being ok, and the problem doesn't come back, you
may want to write up a quick conclusion for the list, so anyone else
with the same problem can have an easier time of finding it in the
archives.

Greg Roa

===========================



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