meprntr1 Posted March 31, 2006 Share Posted March 31, 2006 If a knock sensor would be bad would the CEL come on? Quote Link to comment Share on other sites More sharing options...
idosubaru Posted March 31, 2006 Share Posted March 31, 2006 it's easier to talk in terms of your circumstances, what is happening? to try and answer....it could and it is designed to do that. but that doesn't always happen. it is possible to have a bad sensor but not throw the CEL. that shouldn't happen, but it can (though rare). Quote Link to comment Share on other sites More sharing options...
meprntr1 Posted March 31, 2006 Author Share Posted March 31, 2006 When I acclerate or go up hills I have a slight knock/ping. It seems to happen as the engine gets warm. I have a 05 Impreza 2.5 RS SW. I have had it to the dealer but they can't seem to hear it. This is the not he 1st time I brought it to their attention. I have also changed fuel octanes but that didn't seem to help. Quote Link to comment Share on other sites More sharing options...
nipper Posted March 31, 2006 Share Posted March 31, 2006 Knock sensors have really two failure modes. The housing cracks or they short to ground. The knock sensor is a peice of quartz tuned to the harmonics of the engine. They generate a small AC signal that the ecu translates and fiddles with the engine timing. What you may be hearing is a light pinging, which is unavoidable in some cars. With todays crappy fuels, ethenol, and god knows what else.... Also the engines today run very lean. Next time you hear it, try a few things. Downshift (it should go away), to change the load on the engine. Turn the ac on (again change engine load), or off depending upon what its on when it starts pinging. Do you notice any smoke out the back of the car. Its hard to tell you to ignore it without driving the car and hearing it myself. Some ping is acceptable (from an engine design point of veiw), and it sounds like you are within that area. Also try amaco or bp mid range, as they are true mid range fuels and not a blend. nipper Quote Link to comment Share on other sites More sharing options...
jamal Posted March 31, 2006 Share Posted March 31, 2006 I had a bad knock sensor and my CEL would come on for a few seconds and then go out, and I was getting some strange hesitation from low RPM. When I replaced the sensor it went away. It's code 22 on an odb1 car by the way. Also my knock sensor was $48.18 from subarugenuineparts Quote Link to comment Share on other sites More sharing options...
cowboyFunkie Posted April 1, 2006 Share Posted April 1, 2006 I had a faulty knock sensor for over a year on my 96 OB, kept tripping the CEL and I'd just clear it evertime with OBD2 diagnostic program loaded on my laptop. I eventually shelled out the $100 for a new knock sensor and the problem went away. CF Quote Link to comment Share on other sites More sharing options...
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