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  #1  
Old 10-26-2001, 10:51 AM
JC Z28
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Question Knock Sensor Replacement and another Q

How time consuming and dificult is it to change the knock sensor buried under the intake manifold? From the looks of it its as hard as changing plugs on my camaro, damn near impossible. What tools to use?

2nd Question: Recently my SVX has experienced hesitation during start-up. I turn it over and nothing, i do smell gas though. Seems like the car is not gettting a spark but everything including the wires look fine???

Thanks
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  #2  
Old 10-26-2001, 10:56 PM
JC Z28
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Some one??? I know your out there? any of the questions please!!!
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  #3  
Old 10-26-2001, 11:39 PM
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Knock sensor

Knock sensor is fairly easy to replace. What i had to do was
1) remove belts
2) loosen alternator to allow it to swing up. I don't remember what connectors I had to disconnect, but I know it was just the easy snap ones, nothing serious. When you swing the alternator up, there is a black peice of flat "conduit" around the wires leading to the alternator. That will have to be left there and bent up with the alternator. It is fairly flexible. I did crack mine, but it wasn't a big deal to me. The job would be even easier if you just removed the alternator, but you don't have to.
3) Loosened the bolt holding sensor in place by turning it with a 12??? mm wrench. A socket wrench won't fit in the space. Use a regular wrench. Once I broke it loose I had to slowly turn it the rest of the way using my fingers....that was the hardest part.
4) Take out bolt and sensor.
5) Put bolt in hole of new sensor and GENTLY set sensor in place so that bolt lines up with its hole.
6) CAREFULLY tighten bolt with fingers. If you are not careful the sensor will move and you'll have to take it out and line up the bolt again.
7) Tighten bolt with same wrench and put back everything you took out/loosened



A lot of this will seem vague until you get in there and do it. If you have any more questions, just ask.

Mat-1
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  #4  
Old 05-19-2002, 07:00 AM
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I pulled the knock sensor closest to the front of the engine yesterday and noticed that the plastic housing on it has a couple hairline cracks in it. Nothing else looked damaged. Maybe this is just from being heated and cooled for 159k miles. Will this cause a different signal - possibly retarding the timing when it shouldn't be? I have never had a CE light but I do notice that sometimes the car feels like its dragging an anchor and other times it erupts out of a turn much faster than I expected. I didn't check the rear sensor because if I'm going to bust apart my knuckles removing that one there's going to be a brand new one going in.
Any ideas?
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92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles
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  #5  
Old 05-19-2002, 07:38 AM
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The best advice I can offer is .....maybe. Subaru doesn't have much to say about testing them (at least not in my book) other than to check them with an ohm meter. Spec is:

Connector & Terminal/Specified value No. 1 - Body/Approx. 560 K ohm

That's not too insightful though. If you have access to a high end graphing meter you could hook up to the sensor and rap (not beat the beejesus out of ) the block nearby and watch for voltage generated. The best method would be to use a scanner and watch it while someone else was driving.

BTW, knock sensors should always be replaced in pairs.

Applicability: 1992-1995 SVX 3.3L

FAILURE CODE OPERATION # LABOR DESCRIPTION LABOR TIME

KNOCK SENSOR A145-581 KNOCK SENSOR BOTH-REPLACE 0.7
UEA-48 (INCLUDES ACCESSING DTC
USING SELECT MONITOR)

Note :Refer to revised 1992-1995 SVX 3.3L knock sensor replacement information on the reverse side.

Revised SVX Service Manual Removal And Replacement Procedures For Knock Sensors Number 1 (RH) and Number 2 (LH). This information supersedes the Removal And Replacement Procedures listed in the SVX Service Manuals.

Removal

^ Disconnect negative battery cable
^ Remove both plastic intake manifold covers
^ Remove the alternator


Left Sensor Replacement

1. Disconnect the knock sensor wire connector.
2. Note the orientation of the knock sensor on the engine block and install the new sensor in the same position.
3. Use a 3/8 drive ratchet, 12 inch extension and a 12 mm flex socket to access the knock sensor mounting bolt.
4. Insert the extension and socket assembly through the left side of the hole in the center of the intake manifold, refer to the illustration below.

Note : When removing the knock sensor, the wire connector is tight but will pass between the coolant crossover manifold and the engine block.

Right Sensor Replacement

1. Disconnect the knock sensor wire connector.
2. Note the orientation of the knock sensor on the engine block and install the new sensor in the same position.
3. Use a 12 mm boxed end wrench to access the knock sensor mounting bolt from the front of the engine.


Installation

^ Install in reverse order of the removal procedures

Note : Torque the knock sensor mounting bolt(s) for all applicable models to 17.4 +/- 2.1 ft-lb.
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  #6  
Old 05-19-2002, 08:48 AM
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Why is it slow than fast?

Quote:
Originally posted by immortal_suby
but I do notice that sometimes the car feels like its dragging an anchor and other times it erupts out of a turn much faster than I expected
My car does this also. It is it really possible that the knock sensors are the cause?
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  #7  
Old 05-19-2002, 10:03 AM
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They could be. But I remember my '92 when it was new and it was the same way. Kind of similar to a big japanese bike, it would 'jump on the pipe' at about 3000rpm and have a huge surge of power. I have since attributed it to the programming in the ECU. My '94 has much more 'linear' power curve, and not quite as much power at that. The '92 was more of a wild-child...
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  #8  
Old 05-19-2002, 12:35 PM
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Strange thing is my wife's 92 seems to always have enough power. It jumps off the line fast and pulls strong every time. It is like driving a pontiac - it jumps the second you hit the throttle. I catch her and pass her in the top end but she always gets the jump off the line. It is really annoying.
I will have a case study complete next week with mine - 2 knock sensors are on order from 1stsubaruparts. Only $31 each - I didn't know they were that cheap.

Thanks for posting the service manual notes, Beav.
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2015 BRZ Limited 6MT
92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting
92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles
19 Subaru Ascent Premium - -Hers !.
89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P.
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  #9  
Old 05-19-2002, 01:17 PM
sith
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Immortal - you could try swapping the ECU from your wifes SVX into yours and see how the behavior changes. Are the two manufacturing dates significantly different?
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  #10  
Old 05-20-2002, 04:44 PM
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I've swapped them twice. The dates are 6/91 and 1/92. Her's has a factory chip in it and mine doesn't. It didn't make a difference with either ECU that I could tell.
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2015 BRZ Limited 6MT
92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting
92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles
19 Subaru Ascent Premium - -Hers !.
89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P.
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  #11  
Old 05-20-2002, 09:32 PM
billisa
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Hesitation?

There is a TSB related to this that says you should crush the PCM, after wrapping it in black tape, not remove it altogether. Check it out on Alldata. It may not be the PCM you're crushing, but a component near it.
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  #12  
Old 05-20-2002, 09:36 PM
billisa
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Here's the TSB Is this relevant to your problem

ECM - Hesitation on Acceleration

NUMBER: 11-44-93

DATE: 10/04/93

APPLICABILITY
1992 AND 1993 SVX

SUBJECT:
SVX ACCELERATION LOGIC CONTROL

The SVX ECM has a built-in logic which controls the vehicle acceleration from a standing start. The logic controls the power during light to medium acceleration. THIS CONDITION IS "NORMAL", and no repair attempts should be made to change it. This condition is sometimes mis-diagnosed as a hesitation.

If a customer complains of a hesitation and it is not the normal condition as described above, make sure the customer is using premium fuel. A check of all basic engine functions should be performed to make sure they are all normal. If all engine functions are found to be normal, follow the procedures below.

CAUTION: BEFORE WORKING ON THE ECM, REMOVE THE STATIC CHARGE FROM YOUR BODY BY MOMENTARILY TOUCHING AN EARTH GROUND, SUCH AS: A COLD WATER PIPE, METAL BUILDING SUPPORT BEAM OR A CLEAN, METAL AREA OF THE VEHICLE.

1) Remove the ECM from the vehicle and remove the six screws securing the cover of the ECM.

NOTE: If the ECM has a ROM installed into the ROM socket, the tan resistor should be cut and/or removed. (See Service Bulletin 02-87-92).






2) Locate the black noise suppressor as shown in Figure 1.

3) Wrap the noise suppressor with electrical tape.

4) CAUTION: SAFETY GLASSES MUST BE WORN DURING THIS PROCEDURE. Holding the ECM upside down or on its side, grasp the black barrel shaped portion of the noise suppressor with needle nose pliers. Slowly squeeze the noise suppressor until the barrel shaped portion is crushed. "DO NOT USE A TWISTING MOTION." Be extra careful not to cut the wire which runs through the center of the suppressor. If the wire is cut or broken the ECM must be replaced.

5) Holding the ECM upside down, remove the tape from the noise suppressor and lightly shake the ECM to make sure all the crushed particles are out of the circuit board.

NOTE: IF THE ECM DOES NOT HAVE A ROM INSTALLED INTO THE ROM SOCKET, DO NOT CUT THE TAN RESISTOR.

6) Reinstall the ECM into the vehicle, and clear the memory using the select monitor.


A modified ECM will be incorporated in production beginning with 94MY vehicles. Modified ECMs can be identified by a black dot next to the parts number label.

FLAT RATE INFORMATION
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  #13  
Old 05-21-2002, 04:38 PM
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I crushed the noise suppressor a long time ago - right after buying the car at about 100k- I remember at the time seeing a big difference. So far this week after just cleaning up the one knock sensor the car has been way better. Maybe I broke the thing and its running fully advanced. I have to run a little while longer to know for sure, its also been about 20 degrees cooler than usual here which could be the difference. I still didn't see a difference between either ECU after one had the noise suppressor crushed - in either car- the 6/91 ECU doesnt even have a noise suppressor - pics are in my locker of the difference between the 2 ECU's.
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2015 BRZ Limited 6MT
92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting
92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles
19 Subaru Ascent Premium - -Hers !.
89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P.
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  #14  
Old 06-23-2003, 08:16 AM
nikkihorz
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Interested in what happened

Just wondering if you were going to post what happened when you replaced the knock sensors. One of mine is sending out an error code and I am experiencing hesitation and surging when cold.

Thanks. It would be great if you reply.
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  #15  
Old 06-23-2003, 04:57 PM
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Replaced them both and car runs fine. No hesitation but still have the annoying svx trait of taking off very fast sometimes and seeming to drag an anchor others. Its better than before but it is still there sometimes.
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2015 BRZ Limited 6MT
92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting
92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles
19 Subaru Ascent Premium - -Hers !.
89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P.
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