16v missing/misfiring (long)

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Hi,

Recently I've been experiencing some problems with my '87 16v. A
little over a week ago I changed the valve cover gasket to fix oil leaks
including cracked spark plug sealing rings that were causing my spark
plug boots to emerge from the engine completely covered in oil. In the
process, I removed the intake manifold and the valve cover, cleaned
everything up with lots of carb cleaner, and reassembled the valve cover.
Before putting back on the intake, I removed the distributor cap to use a
dremel brush to clean off corrosion on the arc points. I reassembled the
distributor, and then the intake, etc. When I went to start the engine, it
wouldn't catch. I quickly discovered I had failed to seat the distributor
cap completely on the housing. After clipping it in properly, the car 
finally started. However, ever since it has been missing about 1/8th of
the time. This percentage increases when it is cold or at a low rpm. The
missing creates a real power loss at pretty much all rpms, and I'm of
course concerned about what is causing it.

My distributor has been leaking oil for some time. Realizing that this was
most likely an ignition related problem, I splurged and bought a new cap
and rotor and installed them. Motor started and ran, but just as bad as
before. A test drive revealed that it had a bit more punch than before
(probably because the old rotor was missing the metal clip that keeps it
from rotating slightly! oops!), however, it was still missing.

When I bought the car and changed the timing belt, I pulled out the spark
plug boots to remove the plugs so I could crank the engine by hand to TDC.
I discovered that the bottom of plug boot #2 was "bitten off". There was
literally a chunk missing from the bottom. I can't tell if it is arcing
there or not, but one of my hypothesises (is that a word?) is that the oil
that leaked all over the spark plug well had been insulating the spark
plug boot and keeping it from arcing. Now that I cleaned it up, perhaps
the spark is going to the head instead of the spark plug. Unlikely, but
possible.

So I looked at plug wires. $100, $120... $35,000 (financing available)
Too expensive to get without knowing the old ones are shot. I misted them
at night with the engine idling and nothing special happened, no change in
engine sound. Still missing. I plan to swap them with another 16V owner to
test if they are the culprit, but I haven't had good weather or a garage  
to do so.

The plugs, cap and rotor are new (<2000 miles), the distributor, plug
wires and coil appear to be original. The distributor has been filling my
engine compartment with oil, and the clip-in suppression shield that
slides onto the distributor shaft just before the rotor does is all chewed
up, don't know how that happened. I plan to check the hall sender
connector, although a p.o. lost the screw that holds the connector to the
distributor housing and its being held on with a zip-tie. I'm afraid to
touch it.

I think the coil being faulty or a fuel mixture problem are both unlikely,
but not rule-outable (another invented word, yay) because I didn't touch
either of them when changing the valve cover, which is when the problem
began. The only thing I can remotely think of is that me spraying carb
cleaner inside the tb plenum and on the mating surfaces of the upper and
lower intakes, as well as all over the valve cover and the head somehow
is richening the mixture beyond all limits. I used "oxygen sensor safe"
carb cleaner, but maybe the oxygen sensor is sending a false rich signal
to the ecu which is in turn leaning out my mixture ? I don't know.

Anyway, I'm debating what my next step will be after these tests if they
fail to determine a definate or likely cause:

1) Buy a new distributor for $175
   Pros: old one is worn out, this is brand new, bosch, suppression shield
         isn't chewed up, even if it doesn't fix missing it will fix oil
         leak.
   Cons: expensive as hell, difficult to install ?

2) Buy new plug wires for $120
   Pros: silicone insulation won't crack, will be able to rule out spark
         plug boot chomp in later problems, get to pick pretty colors
   Cons: expensive, i'd rather not spend the money if this isn't the 
         problem

I was thinking for a while that my hall sender was the problem, but if I
remember correctly these tend to die all at once, right? Would a dieing
hall sender cause this kind of missing but still let the car be drivable?
I remember reading that the connectors on both sides for the hall sender
have flakey insulation that lets oil in, and teensy wires that break and
cause problems. Has anyone had a similar problem and found out it was the
hall sender.

Thanks for your feedback,

-Toby

--
'87 16V

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