I've heard people from this group saying there's a knock sensor on 04 Forester that went bad sometimes. I asked the same question to my mechanic and told him that I put in regular unlead gasoline as recommended on the manual. He said cars with knock senser should use premium gas or else the function of the sensor would be useless. Cars without knock sensers can use any type of gas. Is that correct I wondered? He means there's no point putting in a knock sensor if regular unlead is used. The knock sensor will become faulty if you keep using regular unlead instead of premium gas.
Knock sensor on 04 Forester
Jun 25, 2004
3 Replies
Hi, That is pure B.S. Tony
The knock sensor in my old 97 Neon DOHC was used (among other things) to change the enginge performance. (via engine timing?) If you ran it on regular the sensor adjusted the engine computer so that it would run well on the economy fuel. If you used super it adjusted the engine (via the lack of knock) for more performance. According to Plymouth (RIP) the horsepower changed from 135 to 150 based on the knock sensor input to the computer.
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