Re: Need Help From the Experts (Shawn, Andy) or Anyone Else

[skerocdriver@juno.com (Shawn C Meze)]

On Tue, 18 Nov 1997 05:04:39 -0800 "Smokinn"
<smokinn@crestview.sbceo.k12.ca.us> writes:
>Thanks Shawn,   I checked the knock sensor system (test from Haynes
manual)
>by performing the test with a test light.  It checked out fine according
to
>the manual, however it does recommend having it checked out by a
computer
>test unit if the test doesn't pass.


Hmmm......
OK, well looking at my GLi 16V section (Don't have a Scirocco Bentley,
just the Jetta Golf Bentley. See kids! Another great gift idea for this
xmas that you can get me!! ) on testing the KS system, it shows to first
check the ignition coil and the transistorized Hall Sender unit. 
After those 2 are OK, you can check the control unit by removing the
harness connector from the KS control unit. 

Ign switch to ON.

Measure the voltage between terminals 3 and 5. You should read approx
battery voltage. (Looking at the connector terminals with the clip facing
to your right. #1 is top left, #8 is top right. #9 is bottom left, #15 is
bottom right.) 

Next measure voltage from terminals 6 and 3. Again, you should read
approximate battery voltage. Leave the leads there and open the throttle.
Voltage should drop to zero. (Oh, your testing the idle switch. I get
it.) 

Next test terminals 3 and 8 and go Full Throttle. (testing the FT switch
now.) You should get battery voltage at full throttle. Reinstall the
harness to the KS unit.

Hmm, I didn't see anywhere there that we tested the KS box itself. Ok,
whatever.. 

Next, remove the Hall Sender connector (at the distributor) and with the
key on, check the 2 outer terminals. You should have a 5 volt minimum. 

OK, this one is a toughie. Might require 2 people. Might not depending on
what kind of test rig you have. Here goes.
Ign switch OFF.
Connect your miltimeter to the (-) terminal and (+) terminals. With a
wire, connect the center terminal of the Hall Sender connector briefly to
ground it while watching the volt meter on the coil. The voltage should
increase briefly to 2 volts, minimum. If not, replace the KS control
unit. Oh, this is where we test the box. Cool.

Next, redisconnect the harness connector from the KS control unit.
measure the resistance between terminals 13 and 14. 

I Don't know how to determine whether or not you have the type I or the
type II sensor types, but you should read either:
Approximate 300 K-Ohms on the type I
Approximate  Infinity Ohms on the type II

Reconnect the harness connector from the KS control unit.

The next bit of testing requires a test LED light. (US 1115). This really
makes me want to own EVERY piece of specialized test equipment so I could
check EVERYTHING. Then id have to change my e-mail address to
DrScirocco@juno.com!!! Doh!!!




>If I drive his car at about 30-35 mph, running at about 3k RPM +, it
will
>tap, but if I let off the throttle just enough to maintain a steady
>speed...it stops and doesn't tap anymore until I press the accelerator.


That still really sounds like ping to me. Ping sounds like a high pitched
rattle. Rod knock sounds like..... rod knock. Piston slap sounds more
like ping that rod knock.

What about first gear, where the load isn't so severe. From a rolling
start, low rpm, jump on the throttle. Does it ping?? It should'nt since
the load is low but if its piston slap or rod knock,  you will hear it. 
Not only that, the knock will get worse and worse as you drive the car.
Piston slap and rod knock are pretty much terminal for which ever part is
failing. Id leave it alone for the next couple days and keep driving it
and see if it gets worse or not. Don't drive it to the point it seizes on
you. That's no fun and not worth the extra expense of buying another
crank because the bearing spun. 
If it is rod knock, you will be able to hear it at idle and as engine
speeds increase, the knock gets louder with it. 
Tell me, what's the water temp of the car?? Does it run hot?? 


>talked to one guy who believed it to be "piston slap", but doesn't
piston
>slap normally apply to race cars and goes away after the engine is warm?
>Gerry


Yeah, piston slap is usually a light piston that is a bit smaller than it
should be than the cylinder walls. The idea is that the piston will heat
up, grow a little and full the cylinders a bit more. The slap is the
piston skirts hitting the cylinder walls on the detonation stroke. It
typically goes away with the increase in engine temps. 
Then again on an older motor, if the rings are gone, you can get piston
slap when the engine is somewhat hot. I Don't think this is the problem.

Well, HTH!!



              Shawn Meze
86' Jetta GLi           82' Scirocco GTi
The Fastest, Quickest, Cleanest and
best looking Scirocco in all of San Diego!
http://home1.gte.net/vwfan/meze/hello/
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