Re: 16v missing/misfiring (long)

[T Berk <tberk@mindspring.com>]

archive@porknet.fdns.net wrote:

Love the ISP. :)

Disclaimer; I am a mk1 8v kinda guy.

> 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  <snip>
> 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.

This sounds like a case of Dremel Tool gone bad. Metallic particles in
the cap will lead to electrical tracks that can cause arcing and
misfires. Don't tear up inside the cap, or on the plugs, themselves too
much.

>  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. 

This might have caused the damage to the shield inside the dist.

> 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.

This is a direct example of poor and/or misguided spark. Other than air
leaks, (you _did_ remove the intake), the dist cap, roto, and Hall
Sensor are now suspect. Arcing as you ponder around the plug boots can
be remedied by applying dielectric grease to the boots' interiors. This
will help seal the boot to the plug body. It doesn't take a lot, just a
light coating.

> My distributor has been leaking oil for some time... 
> I splurged and bought a new cap > and rotor and installed them. 

Now we're talking!

> 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.

Newer rotor don't have the metal part inside that fits into the groove.
They now have a molded part that fits into the cut into the dist. shaft.

> 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.

This may be the culprit. Surely it was bumped of moved or something
during the prev. procedures.

> I think the coil being faulty or a fuel mixture problem are both
> unlikely, but not rule-outable (another invented word, yay)...

Me neither. (Love invented words. Keep up the good work.)

> 
> Anyway, I'm debating what my next step will be after these 
> tests if they fail to determine a definate or likely cause:....
> 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? 
[NO]
> Would a dieing hall sender cause this kind of missing 
> but still let the car be drivable? 
[YES]
> 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. 
[TRUE] & [TRUE] 
> Has anyone had a similar problem and found out it was the
> hall sender.
> Thanks for your feedback,
> -Toby
> '87 16V

I had a flaky Hall Sensor connector that caused the car to miss, then
fail to run at low RPMs and finally failed all together just as i rolled
into the parking lot at work.

They DO have funky little wires that pass enough signal on a good day
but can _look_ OK but not pass a good signal after all the heat and time
have had at them. You should clean out the connector and spray some
Electro-Lube or Dielectric grease or Stabilant 22 in there. 

Distributors have seal kits or you could just replace it altogether.
Gotta stop the oil leak somehow though. 
They are not hard to install if you are replacing the whole thing,
marking were the original is prior to removal will help. You will want
to retime the car after installation but it could be part of a regular
tune-up done by a competent shop if you wish.


hth,
TBerk


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