speed and reference sensor '87 5ktq - test?

[Ben Swann]

On Wednesday, August 21, 2002 12:59 PM, Ben Swann
[SMTP:bswann at worldnet.att.net] wrote:
> Patient: '87 5000 Turbo Quattro
> Symptom: hesitation at high load, boost and RPM
>
> I am following upon a check engine light 2111 code pulled which
corresponds
> to the RPM/speed sensor.
>
> I have also been having a symptom of hesitation at higher load and RPM(3k
> on up).
>
> I installed new plugs cap and rotor which helped, but there is still some
> hesitation at 1.3 bar on up to 1.7bar - yes the car has a mod.  This
> symptom has been present on the car since I purchased it 10 months ago,
and
> I'd like to get rid of it, even though the engine otherwise runs fine.
>
> I pulled out the reference and speed sensor assembly to clean, and there
> appears to be some physical damage - particularly the speed sensor is
> dented, and you can turn the sensor with respect ot its connector.
>
> So although I will likely get a replacement, can I check to see if these
> are still good even though they appear damaged?  There was a bit of crud
to
> clean, and some metal filings held onto both sensors magnetically which I
>  suspect could have contributed to faulty operation.
>
> Ben
>
[OK - Now I cleaned the sensors and re-installed.

I now consistantly get a 2142 - knock sensor.  Also a second code of all
blank occurs when I insert fuse a second time - end of diagnosis or ???.

Does someone want to confirm any bad news or perhaps give me some good.

Ben]

[To: quattro at audifans.com
From: Ameer Antar <antar at attbi.com>
Subject: RE: speed and reference sensor '87 5ktq - test?

Try and clean up the connection to the ECU harness, which is in the bracket
of 3 connectors in the middle of the firewall. There may be corroded
contacts or just a loose connector. Also I'd check the wiring to the sensor
all the way from the ECU, and even loose connections at the ECU. The SJM
website has the pinouts for the ECU so you can find the ones for the
ref/timing sensor. Maybe test w/ an ohm meter and have somebody move the
cables in areas prone to vibration. Check the meter for any fluctuations,
but make sure your just not loosing contact to the meter.

Make sure the ECU light doesn't stay on for long, b/c the engine is pinging
and can hurt itself. Try reducing the boost, or higher octane, at least
temporarily till you figure this out. Good luck.

-ameer]

Well I almost went down the path of methodically isolating, checking and
cleaning the components as the codes would appear.  Seems I'd check one and
then get a new fault code.

Chris Semple took a SWAG at suggesting I swap the ECU.  So I did.

Looks like I've been driving around with a bad ECU for some time, only it
just got more and more flaky.

Found the fuel pump relay lead pin 21 wired to ground - looks like someone
installed a Charlie spring(good), but no chip, which is what I had
suspected, just never got around to checking - my wife didn't even notice
cause she doesn't put the foot down.

Car still has some hesitation at boost, plugs, cap and rotor helped.  I
suspect this is the characteristic of overriding the ECU fuel pump shutoff
and not using proper fuel/timing maps.  I did not notice this problem with
the resistor mod though on my other '87 5ktq avant.

Anyway, now 1 QLCC chip is destined for this car for a properly controlled
1.8 bar.

Ben

p.s. car is for sale, so I'm working out any niggles:
http://www.homestead.com/ben_swann/Char5ktqa.html