[xj-s] Spark knock?

Just bought a 94 6cyl, and practically can’t hear my kitten purring
over the knocking, even at moderate acceleration levels (under 2500
rpm). Not so tech savvy, but definitely willing to learn.

Is there anyway to muffle it without affecting performance?

Using strictly high octane. Tuning/timing perfect according to
local dealership.–
Still lovin my '94 XJS 4.0 6cyl
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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In reply to a message from rmedecke sent Wed 4 Jan 2006:

I also have a 94 4l (2+2) and have never had this occur anywhere in
the RPM band, even when I’m running 91 octane. Heavy knock can
trash an engine and is not something you can muffle or ignore.
The 94’s do not have a knock sensor, ECU controls fuel and injector
pulse and timing based upon demand curves preprogrammed in. What
extent was your tuneup, and under what conditions are you driving.
I would normal think (and chase) plugs, injectors fouled, wires,
distributor cap or rotor, O2 sensor, air or fuel filter, then start
getting serious about camshaft and valves. If it only at low RPM
and does not occur at higher load and RPM that would seem to rule
out many of these things. If the local Jag dealership did the
tune, take it back and ask that a mechanic take a test drive with
you.

Bill Miller

94 2+2 XJS
87 XJ6–
The original message included these comments:

Just bought a 94 6cyl, and practically can’t hear my kitten purring
over the knocking, even at moderate acceleration levels (under 2500
Using strictly high octane. Tuning/timing perfect according to
local dealership.


w156
Granger, IN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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The EGR malfunctioning will cause spark knock. Did
the dealer(?) upgrade the ECU software?— w156 williamjm156@comcast.net wrote:

In reply to a message from rmedecke sent Wed 4 Jan
2006:

I also have a 94 4l (2+2) and have never had this
occur anywhere in
the RPM band, even when I’m running 91 octane.
Heavy knock can
trash an engine and is not something you can muffle
or ignore.
The 94’s do not have a knock sensor, ECU controls
fuel and injector
pulse and timing based upon demand curves
preprogrammed in. What
extent was your tuneup, and under what conditions
are you driving.
I would normal think (and chase) plugs, injectors
fouled, wires,
distributor cap or rotor, O2 sensor, air or fuel
filter, then start
getting serious about camshaft and valves. If it
only at low RPM
and does not occur at higher load and RPM that would
seem to rule
out many of these things.

// please trim quoted text to context only

In reply to a message from rmedecke sent Wed 4 Jan 2006:

Perhaps will make more sense if I describe the noise. On
acceleration, cold down to 1000rpm but always above 1500 rpm,
sounds like a gigantic card taped to bike frame slapping the spokes
as the wheel turns.–
Still lovin my '94 XJS 4.0 6cyl
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

// please trim quoted text to context only