False Knock Counts
Thread Starter
Heel & Toe
Joined: Oct 2002
Posts: 24
Likes: 0
From: Whitby Ont.
False Knock Counts
Just how sensitive is the factory knock sensor and ESC module? Would forged pistons and roller rockers cause false knock counts with a MAF TPI setup? I know that on really cold days my forged pistons rattle for the first 30 seconds or so of run time until they expand since they are run with more clearence than a cast piston and forged units expand and contract much more than cast. Even though there is no audible noise once they have run for a bit, I assume they still make more noise than a cast piston. I also assume that roller rockers will make much more noise than factory stamped rockers do. If this is going to be a problem is there someway to desensitize the knock sensor a bit so it overlooks the piston and valvetrain noise that comes with these aftermarket parts? Thanks.
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Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: False Knock Counts (Chevyguy1984)
My stock '84 Crossfire was getting false knock signels sent to the ECM. As a "final" test, I drained the tank, filled it up with 91 octane (best we can get up here) and revved it in neutral, with a scanner attached. The scanner received knock counts. I had never heard any pinging, even on 85 octane, so I diconnected the sensor from the ESC. I now rely on the tried and true audible method of detecting ping. Anything that rattles on or in the engine will set off the sensor on the early cars. Because of my stock internals, I had to assume it was a worn motor mount or some other innocent cause. Loose pistons, roller cams and lifters, and a good roller timing chain can all contribute to "false" knock signels. Later engines have most of the above items, and I understand that "The General" has a less sensitive ESC, that it used on the later engines. Look under the "Tech Tips" section and I believe you'll find a how to, with part numbers and all. To me, there is little worse than having your ECM retard your spark, for no good reason. Good luck and...
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