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Old 09-01-2011, 03:11 PM   #20 (permalink)
wstar
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Quote:
Originally Posted by Zat_Zuma View Post
My best guess is that the ECM is cutting the fuel to the injectors and partially closing the throttle bodies from a false reading from one of the sensors. This may be what is causing the lean condition to cause knock.
The engine should never knock if the ECU cuts fuel. The ECU cuts fuel in the same way for all of its engine limiting (the normal rev limit, the limp mode rev limit, VDC) as well as anytime you engine brake. When it does this, no fuel is injected at all, and the cylinder becomes an air pump. There's no lean burn happening (or shouldn't be, barring some failure). I believe in most of these scenarios there's a soft limit first, which basically modulates the drive-by-wire throttle input (like lifting the gas pedal), then a harder limit where it cuts out fuel delivery.
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Last edited by wstar; 09-01-2011 at 03:13 PM.
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