more on 16v knock sensor diagnosis

[treed2@u.washington.edu (T. Reed)]

John,

The jury is out on whether my knock box is the problem.. here's the
evidence:

Guilty:
- the car has no pull off idle
- the timing must be fully advanced (beyond 6 deg) for the car to run good
- unplugging the knock sensor doesn't change anything
- the knock brain has stopped supplying the fuel pump relay with a ground.

Innocent:
- knock brain test with led test light in bentley reports 'no faults'
- the hall sender, which is necessary for the car to operate at all, is
  routed through the knock brain and solely the knock brain. So, if the
  knock brain was -completely- fried, the car wouldn't drive.
- primary coil resistance is out of spec

So, right now its still looking like guilty.. but I'd like to find a
bloody glove before I go sink a lot of dough in to a new knock box.

The other possibility I can think of is that its not spark .. but fuel. I
say this because I pulled my fuel distributor to check the plunger for
binding and its a bit murky on the first bit of travel (perhaps 1k-2k
rpm). It takes a good amount of force to get it to move initially.
Cleaning didn't help.. but I don't know if its supposed to be this way or
I'm just on crack..

> Its been a year, I have small children...  It sounds like
> pin 10 is the correct one to test the relay function.

The only thing I'm concerned about is blowing up my other computers or
making it so that I can't drive at all.

>  However, you should have continuity to ground on 12 with
> the ignition on (verifies signal coming from the ICM).

Hmm, okay.. I'll check it out.

> Your coil test is interesting. The secondary winding on a
> 16v car should test between 4800-6800 ohms.  Did it test
> that high?   I would be surprised.  You can't buy a VW
> coil that will.  You have to go aftermarket for a high
> voltage coil.  (This is OT to the topic, though).

I don't understand what you're saying here.. I'm 90% sure my coil is
original.. is there a typo in the Bentley ?

Here's what I know:

PL (Scirocco 16V):
			Bentley Spec		My Coil
==========================================================
Primary		|	0.6 to 0.8 ohms		1.0 ohms
1(-) and 15(+)	|
----------------|-----------------------------------------
Secondary	|	6500 to 8500 ohms	7830 ohms
15(+) and 4	|
----------------------------------------------------------


> Have you ever checked the mixture at idle?  I've found
> that an out of spec setting hurts the low end significantly.

Yes, I've set it to 10 mA +/- 1 mA. My idle is smooth and steady after
warmup (but during warmup it ping-pongs between 500 and 1300 as it nearly
falls on its face and then bounces back). The oxygen sensor voltage is .7
volts +/- .05 volts.

> John
>

Thanks,

-Toby