beopots Posted September 3, 2009 Share Posted September 3, 2009 hey guys. I've got a 97 legacy outback which had the CEL come on intermittently, had it checked and it said it was the Knock Sensor. Being the cheap guy that I am, I let it go, thinking it would go away with some seafoam or injector treatment, or at best, remain inconsistent. Now it runs very rough at idle and when I drive it to work, 20+ miles freeway speeds, I get to the offramp and it smokes and stinks. (my gut reaction is fuel not being consumed is burning on the cat) The check eng light is now on consistently. It's to a point where I'm afraid of causing more damage, so any ideas/checks for me? Would the knock sensor cause this, or is the knock sensor actually picking something else up? Fuel economy is gone down noticeably as well. Any help is appreciated. Link to comment Share on other sites More sharing options...
joneappleseed Posted September 3, 2009 Share Posted September 3, 2009 I own 2 1996 Outbacks. #1 is a 2.5 auto. It was missing during acceleration in the 2200 to 2700 rpm range. New knock sensor fixed it. Had it installed at what I thought was an honest place. I think they charged so much because they took some parts of to get to it. Like $200 labor. #2 is a 2.2 5sp manual. It was dying at idle. For some time it was hiccupping during accelaration as well, but the idle problem was driving me insane. Last night I pulled the sensor off myself. It had two cracks. Put the new one on and it runs smoother and is no longer dying at idle. I looked at several threads here concerning how to replace. Pretty easy. $65. Thanks for the resource here. Both cars had the CEL code of po325, Knock sensor malfunction. Link to comment Share on other sites More sharing options...
idosubaru Posted September 3, 2009 Share Posted September 3, 2009 yes knock sensor can cause that. all sorts of info on here for how to replace. Link to comment Share on other sites More sharing options...
nipper Posted September 3, 2009 Share Posted September 3, 2009 hey guys. I've got a 97 legacy outback which had the CEL come on intermittently, had it checked and it said it was the Knock Sensor. Being the cheap guy that I am, I let it go, thinking it would go away with some seafoam or injector treatment, or at best, remain inconsistent. Now it runs very rough at idle and when I drive it to work, 20+ miles freeway speeds, I get to the offramp and it smokes and stinks. (my gut reaction is fuel not being consumed is burning on the cat) The check eng light is now on consistently. It's to a point where I'm afraid of causing more damage, so any ideas/checks for me? Would the knock sensor cause this, or is the knock sensor actually picking something else up? Fuel economy is gone down noticeably as well. Any help is appreciated. Replace the knock sensor, clear the codes, and let us know if anything else comes up. How many miles on this car? nipper Link to comment Share on other sites More sharing options...
beopots Posted September 3, 2009 Author Share Posted September 3, 2009 150 + miles. it's seen it's share of roads (and off). Is there any sort of test I can do to make sure it's the knock sensor before stopping by the subie store? Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 3, 2009 Share Posted September 3, 2009 Knock sensor will cause the engine to run in failsafe mode - using more fuel as it retards the timing to prevent detonation. This will lead to catalytic converter failure, fouled plugs, and all the other nice things that go along with running rich. The knock sensor is less than $100 and takes about 15 minutes to replace. Replace it and clear the codes. A bad knock sensor will never go away - it will remain bad and only get worse. It is not inside the engine nor is it subject to fuel, oil, or coolant. No amount of "repair in a bottle" will fix a bad knock sensor. GD Link to comment Share on other sites More sharing options...
nipper Posted September 3, 2009 Share Posted September 3, 2009 Knock sensor will cause the engine to run in failsafe mode - using more fuel as it retards the timing to prevent detonation. This will lead to catalytic converter failure, fouled plugs, and all the other nice things that go along with running rich. The knock sensor is less than $100 and takes about 15 minutes to replace. Replace it and clear the codes. A bad knock sensor will never go away - it will remain bad and only get worse. It is not inside the engine nor is it subject to fuel, oil, or coolant. No amount of "repair in a bottle" will fix a bad knock sensor. GD What he said. Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 4, 2009 Share Posted September 4, 2009 A bad knock sensor will never go away - it will remain bad and only get worse. It is not inside the engine nor is it subject to fuel, oil, or coolant. No amount of "repair in a bottle" will fix a bad knock sensor. Well sure it can... You just have to pour it all over it and light a match. :-p Grab one from a junkyard. Or two. The place I go to sells 'em for like 5 or 6 bucks. Link to comment Share on other sites More sharing options...
johnceggleston Posted September 4, 2009 Share Posted September 4, 2009 The place I go to sells 'em for like 5 or 6 bucks. please oh-wise-one, where do you go to pull your own parts? they don't do that near here, at least i don't know where they let you. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 4, 2009 Share Posted September 4, 2009 Grab one from a junkyard. Or two. The place I go to sells 'em for like 5 or 6 bucks. I haven't had much luck with knock sensor's in pulling used one's. They are cheap and it's better in the long run if I have to replace it once vs. multiple times. They aren't a particularly rare failure so it's just as well that you buy a new one IMO. GD Link to comment Share on other sites More sharing options...
beopots Posted September 9, 2009 Author Share Posted September 9, 2009 i replaced the knock sensor and it has shut off the CEL. also it seems to have plenty more pickup from stops. It still runs rough, but that may be due to the age and miles of the vehicle. The smoking and smell has stopped. In short, it runs better. Thanks to all. I also picked up a few used sensors at the local pick-a-part, if anyone is interested. The plugins were incorrect for my use/year. The subees at the junkyard are pretty picked clean, however, sometimes I can find a gem. Link to comment Share on other sites More sharing options...
nipper Posted September 9, 2009 Share Posted September 9, 2009 i replaced the knock sensor and it has shut off the CEL. also it seems to have plenty more pickup from stops. It still runs rough, but that may be due to the age and miles of the vehicle. The smoking and smell has stopped. In short, it runs better. Thanks to all. I also picked up a few used sensors at the local pick-a-part, if anyone is interested. The plugins were incorrect for my use/year. The subees at the junkyard are pretty picked clean, however, sometimes I can find a gem. Give the car a tuneup, it will run better. nipper Link to comment Share on other sites More sharing options...
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