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Knock Sensor - 2142

Mohammed Bhatti <Mohammed.Bhatti@wcom.com> asked:

	I've got 2142 coming up on my 88 80q.  Bentley says:
	"Defective sensor or sensor wiring.  Check wiring between knock
	and ignition control unit according to wiring diagram."

	A few questions:
	1. Has anyone been through the test procedure for a defective knock
Don't recall a test procedure, but you should check the sensor's mounting
bolt torque and the cleanliness of the mounting surface.  Also, check for a
bad ground connection at the intake manifold, and for water in the CPU below
the r.h. A pillar.

	2. If it's the knock sensor and not the wiring, how much does a
	sensor cost?
Don't know.

	3. What damage do I cause if I continue to drive with a defective
	sensor?  Check engine light comes on sometimes, in particular when
	the car is in stop-n-go traffic or the weather hot.
The knock sensor tells the ignition computer to retard timing to avoid
detonation.  With premium gas, there should be little chance of knocking.
Avoid low rpm full throttle conditions.

	Ok, now for a dumb question:
	What is the purpose of a knock sensor, and why do some have 1 vs 2?
	I assume my 80q has one.
See above.  Audi gods decreed one is sufficient.

Kirby A. Smith   New Hampshire USA
1988 90q Titanium gray, 180 kmi
1988 90q Stone gray, 185 kmi - under construction
1988 90q Stone gray, 180 kmi - under destruction
1995 S6 Pearl effect, 80 kmi