Knock problems

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lucas
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Knock problems

Post by lucas »

Hey guys i tried using the search to remedy a problem I'm having with my wifes car. Its a 93 turbo sedan auto, it was in poor running condition when she bought it. when we got it, it was showing like 8 codes and by process of just fixing things i narrowed it down to two codes. A cam sensor and a knock sensor, I had a old spare cam sensor fixed that no problem.

I then changed the knock sensor with a new one from oreillys lasted maybe 2 months then the CEL began to randomly flash for a few seconds then disappear. It seems to happen more frequently at a stop. I put a new sensor on there same brand did the super computer reset and the problem went away for 1 day then came back.

The car does not run poorly but the constant knock cel concerns me. When i changed it this last time i noticed that some of the plastic wire shielding had been pulled away from the Plug end of the knock sensor from the harness end. I don think a tiny bit of exposed copper would cause that big pf a problem but maybe I'm wrong?

Any help is always appreciated!!!!
thanks, Lucas.
1993 legacy ss "Shela"
cj91legss
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Re: Knock problems

Post by cj91legss »

You can check the resistance between the plug and the ecu. That'll tell you if you should think about running a new wire to the knock sensor. With a little bit of wire exposed, I'm wondering if it's grounding out from all of the movement and triggering a cel.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
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lucas
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Re: Knock problems

Post by lucas »

thats what I'm thinking. I might try cutting the bad end off and getting a new one front the junk yard.
1993 legacy ss "Shela"
Legacy777
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Re: Knock problems

Post by Legacy777 »

Based on my experience that knock sensor wire can be very brittle and there may be cracks that are intermittently connecting/disconnecting causing your problems. I would do what CJ suggested and check the resistance of wire from the plug in the engine bay to the ECU. I'd suggest moving the wire around to see if resistance or conductivity changes.

If you need to replace it, the cheapest and probably best option is to use some shielded microphone cable from radio shack.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
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lucas
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Re: Knock problems

Post by lucas »

I've never ran a new wire like that before but I'm sure the car being as old as it is probably needs a new one. Doing something like that isn't very hard id imagine.
1993 legacy ss "Shela"
cj91legss
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Re: Knock problems

Post by cj91legss »

it's not hard at all. When I ran my new wires, I used the hole under the brake booster. On an N/A legacy, this hole is where the clutch cable would go thru the firewall. On a turbo car there's just a rubber plug there.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT
lucas
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Re: Knock problems

Post by lucas »

word right on, thanks guys
1993 legacy ss "Shela"
cj91legss
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Re: Knock problems

Post by cj91legss »

No problem.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT
Mister Anderson
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Re: Knock problems

Post by Mister Anderson »

Yesterday I replaced my cam, crank, and knock sensor wiring. Make sure you solder the connections and if you can, shrink wrap everything. Harbor Freight sells rolls of shrink wrap and also heat guns for cheap. I picked up some shielded 3 wire at Home Depot for around 40ish cents a foot. The last 3 tubro legs I have worked on all had brittle sensor wire, so it might just be a good idea to replace it anyway.
91 black SS 5 speed (Canadian).... Closed deck EJ20G, fully built, V5/6 sti ra drivetrain, haltech stand-alone
93 silver TW 5 speed... rebuilt 22T with 20G heads, wrx ra drivetrain, otherwise stock.
73 kazen red VW bus riviera camper
lucas
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Re: Knock problems

Post by lucas »

I dont solder things because I've had them break apart. but i do by those nice buttsplices and heat shrink everything. Its still jacked up even though i put a new connector from the harness end on. Still randomly throws knock code it needs a new wire completely and i still have no idea how to do that. Might pay someone to do it.
1993 legacy ss "Shela"
cj91legss
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Re: Knock problems

Post by cj91legss »

Did you already buy mic wire and connectors?
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
91 SS 4EAT Sold!
98 LGT 4EAT
98 LGT Wagon 4EAT
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