I have a 98 Legacy Outback, the check engine light code said I need a new knock sensor, so I bought one. The Haynes Subaru manual says that I need to remove the intake manifold on passanger side of engine to gain access to install the new sensor. Is this true? Man that is a lot of work for such a small sensor with an electrical pig tail. Is their an easier way to install? Any advise will be appreciated. Thanks!

The Haynes manual is wrong. All you need is a long socket extension. Shouldn't take you more then 30 minutes at most.

make sure its good and cool first, you'll thank me later

You don't have to remove that stuff if you have a long extension and maybe a flex joint. I think the bolt securing the knock sensor to the block is a 12mm head. Make sure the mating area to the block is clean. The bolt should ideally be tightened with a torque wrench to the manual's spec. Too tight could crack the sensor; too loose isn't good either.

 

A lot of times service manuals say to remove various parts that aren't really necessary to do the job but make the job easier or safer.

When i replaced mine i didn't clean the rusty surface, and i think i overtorqued it Should i remove it and clean the surface?? Fuel economy is a little better but not by much.

yes

yes

 

ok, any torque specs you can give me?

17.4 +/- 2.1 ft*lb(f).

 

Actually I didn't realize it but there was a TSB out for 1990 THROUGH 1995 LEGACY 2.2L, 1992 THROUGH 1995 SVX 3.3L, 1995 IMPREZA 2.2L for knock sensor codes due to breakage of an internal lead wire.

17.4 +/- 2.1 ft*lb(f).

 

Actually I didn't realize it but there was a TSB out for 1990 THROUGH 1995 LEGACY 2.2L, 1992 THROUGH 1995 SVX 3.3L, 1995 IMPREZA 2.2L for knock sensor codes due to breakage of an internal lead wire.

 

mine didn't qualify.......... What do you mean +/- 2.1? do i just do 17.4ft-lbs. Thendo 2.1? lol.

Thanks for the advise. I appreciate it, especially the part about not having to remove the intake manifold. Regards, Larry (Rooster2)

17.4 +/- 2.1 ft*lb(f)

 

17.4 ft*lb(f) is your target torque. Subaru is saying the tolerance is +/- 2.1. So anything in the range 17.4-2.1 to 17.4+2.1 (15.3 to 19.5) ft*lb(f) is OK.

 

Typically you would set your torque wrench for the target value (17.4 ft*lb(f)), and hopefully if the wrench is fairly accurate and not too far out of calibration, the actual torque will fall within the tolerance.

 

Sometimes you will see them specify different + and - tolerances, such as 134.7 +20 -10 ft*lb(f).

oh I see, ok thanks.

Thanks guys, with a buddy's help, we located the knock sensor. It wasn't the easiest item to find. Now, to get it installed next week. Thanks again to all for the help on this project.

Just tighten it down far enough that it won't fly off and isn't cracked. This isn't rocket science we're talking here.

Just tighten it down far enough that it won't fly off and isn't cracked. This isn't rocket science we're talking here.

 

awesome great advice lol. If i crack it i guess we can just say, hey i could have just got a torque wrench for alot less then a new knock sensor eh?

 

By the way i removed the sensor again, and cleaned the surface with brake cleaner, then used some electronic cleaner and sprayed and wiped the sensor and where it bolts down. Seems to be a little faster. Sometimes at speeds it used to vibrate if i accelerated a bit and not enough. Now the exhaust is just loud lol.

awesome great advice lol. If i crack it i guess we can just say, hey i could have just got a torque wrench for alot less then a new knock sensor eh?

By all means, use a torque wrench if you must. I've spent enough time under the hood to know when something's too tight or too loose. I only use a torque wrench on important stuff like head bolts. The knock sensor is not an overly sophisticated piece of equipment and not having it torqued down to exactly 17.2 lbs/ft of torque isn't going to kill it.

Thanks guys......I successufly replaced the knock sensor. It was a hassle reaching in with a drive extension and flex joint (wobbler) to line up the socket on the bolt head. I used some sticky plummers putty inside the socket to pull up the loosened bolt. I used my torque wrench with poor results, as the flex joint would swivel while using the torque wrench. I just could never get an accurate torque reading. So, I just guess at a good tightness, not too tight to break the sensor, yet tight enough to have it work properly. Car now runs better, the check engine light stays off. Thanks again for all the good advise.

Is it possible that i dont have knocksensor, i looked at several places on the engine where it could be (haynes manual) but no luck yet.

European 2.0 SOCH from a 91 legacy. I also do not have an EGR valve as well (only running 95 octane fuel (lowest you can get here))

Have you looked under the intake manifold on the side of the engine closest to the washer fluid?

best pics I've seen 'round here

location:

removing (note, intake doesn't really need to be removed...that would be more than an hour wasted):

~Erik~

Have you looked under the intake manifold on the side of the engine closest to the washer fluid?

 

Yep but will look again i can not find anything which looks like what i have seen pictured in other posts.