Question about 1997 Subaru Outback
A Knock Sensor allows the engine to run with the ignition timing as far advanced as
possible. The computer will continue to advance the timing until the
knock sensor detects pinging. At that point the computer retards the
ignition timing just enough for the pinging to stop.
A knock sensor assures that you're getting as much power and fuel economy as is possible from your engine.
The knock sensor responds to spark knock caused by over advanced timing. A knock is a sudden increase in cylinder pressure caused by preignition of the air fuel mixture as the flame front moves out from the spark plug ignition point. pressure waves in the chamber crash into the piston or cylinder walls resulting in a sound known as a knock or ping. this is caused by using a fuel with a low octane rating, overheating, or over advanced timing. sometimes it can be caused by hot carbon deposits on the piston or cylinder head that raise compression.
So if the knock sensor is faulty - it sends bad info to the ECM to retar d your ignition. If it is bad enough - the engine will go into an almost "limp home" mode where the RPMs are barely enough to keep the alternator running.
Change the sensor... let it cycle 4 times (hot and cold) then reset the codes.
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Posted on Jul 01, 2009
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Posted on Jan 02, 2017
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