5ktq electrical issues update...

Ameer Antar antar at comcast.net
Wed Oct 1 22:57:09 EDT 2003

I'm not sure what you mean by the knock sensor being voltage-related. Of course the ECU detects voltage from the knock sensor, but this signal is AC, not DC. It's pretty much like a microphone, so the sensor doesn't output a higher voltage when it detects knock, it simply outputs a signal that corresponds to the vibrations it detects. In this system the ECU actually detects for knock through the sensor, much like your brain can listen for knock through the use of a stethoscope The stethoscope doesn't detect the knock, it allows you to hear it; you detect it. Check the knock sensing wires for frays or missing or loose shielding connections. Any noise on the line to the ECU that's the right frequency and amplitude can be interpreted by the ECU as knock. Which reminds me, maybe the RF/IF radiation of the injector control transistors (or FET's, whatever) in the EFI ECU are making lot's of noise for the original ECU at higher RPM. Are they next to each other? Try separating them or shielding the EFI box in a sealed aluminum or steel box. So many possible theories, I know, but this is one of those weird problems... good luck.


---Original Message---
Date: Wed,  1 Oct 2003 16:54:42 -0400
From: "Cody" <Cody at mail.craincorporated.com>
Reply-To: <Cody at mail.craincorporated.com>
To: "Bernard Littau" <bernardl at acumenassociates.com>
Cc: <quattro at audifans.com>
Subject: RE: 5ktq electrical issues update...

The OEM IAT is still in place as it was. The thing about that though was that when I first got the car (back in May) it ran quite bad off of the transporter into the lot here, so I took a look and saw the IAT was disconnected (wires cut), and I have had one of them break on another 5ktq so I knew its effects. I soldered the connection back which as we know didn't help my running issue (same issue still now). Last night I decided to try another sensor from a parts car which didn't help either. I suppose I should ohm out the wiring for the IAT tonight.

What will happen if I just disconnect the knock sensor for a test? I was thinking about the knock sensor before, but I forgot about it. I'll read up on the torque specs and testing procedure in the Bentley right after the shop closes today.

Only trouble with the knock sensor theory is that it its voltage related. I would figure if theres knock sensor issues it would be retarding constantly rather then only when theres enough of an electrical draw. I'll still take a closer look.


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