Knock Sensor Question

[markjw]

1991 Legacy AWD 5 speed wagon.

 

 

If I ignore this Knock Sensor CEL code (22) for a couple weeks, will I regret it later? It showed up a couple days ago. Car runs perfect.

 

 

I suddenly have to split for work in the AM, and I don't have time to fix it. But, I'm leaving my legacy here, at home, and my wife will probably drive it around a little as long as that won't hurt anything. If driving it around is a bad thing, then she won't drive it at all.

 

 

What do you guys think?

[idosubaru]

nope, they often run for a very long time like that. they can rarely cause drivability issues...stumbling, etc...but most of the time just the light.

 

wait 'til it's convenient, nothing to worry about.

Edited November 9, 2010 by grossgary

[markjw]

Thanks, Gary...One less thing I have to worry about.

[idosubaru]

Thanks, Gary...One less thing I have to worry about.

sure. i put these off until i'm doing something else to get the tools out.

[Qman]

Being that you live in the NW and hills are prominent around here. Any detonation will result in a problem. Short and long term. If she is on flat with no hills then there wouldn't be a problem. I wouldn't risk detonation on a long hill or any other time for that matter. But, it is your decision.

[Rooster2]

Being that you live in the NW and hills are prominent around here. Any detonation will result in a problem. Short and long term. If she is on flat with no hills then there wouldn't be a problem. I wouldn't risk detonation on a long hill or any other time for that matter. But, it is your decision.

 

I am under the impression that a defective knock sensor would put the engine computer in limp mode by slightly retarding the timing. Sure the car will keep running, and not leave anyone stranded, but performance and gas millage will suffer slightly. If I am correct, then detonation would not occur.

[Qman]

Limp mode results in low rpm only. Generally speaking, a bad knock sensor will read improperly. It usually will not result in a limp mode. Half the time, the knock sensor is bad long before the ECU recognizes it. It simply can not sense detonation and make the required adjustments.

[GeneralDisorder]

Qman has a good point - you might want to at least get premium when you are at the pump next time if you plan to put it off for a while. That will at least make it a bit harder for you to get into a serious detonation scenario.

 

GD

[mikec03]

Qman may have answered a question I wondered about. I had knocking without any check engine light. i cleaned out the EGR valve, and it seems to have gone away. Maybe the knock sensor is defective?

[idosubaru]

Qman may have answered a question I wondered about. I had knocking without any check engine light. i cleaned out the EGR valve, and it seems to have gone away. Maybe the knock sensor is defective?

if you're getting knocking/questionable noises then definitely check the knock sensor or replace it. it's a frequent EJ failure, i've seen a bunch of them. quite a few things can cause noises so you may want to look into it further.

 

you can inspect them by removing and looking at the base. it's often corroded and/or the outer material is beginning to separate or crack away from the inner metal. they can still "look" okay but still be flawed too.

 

not sure how the FSM says to check them?