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Discussion Starter · #1 ·
Does anyone know the need for a "Knock" sensor on an Intake Manifold? and why does it cost so bloody much? Is it a vital part of the engine?

Its for a 6 cyl. 1985 CJ-7... the dealer wanted $80.00+ for it...

Thanks in advance!

Jon-YJ94
I6, 3.5" Black Diamond, MORE, & more
[email protected]
 
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Discussion Starter · #2 ·
try and aftermarket place like Napa or Car Quest. Shop around, one of your local stores is bound to have one much cheaper.

Nick Hagen
1995 Wrangler
33" Mud Tires and a four banger
 
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Discussion Starter · #3 ·
THe need for the knock sensor is for your on board diagnostic system, without it, your computer will think there is an abnormal circuit, making driving almost impossible. An aftermarket is the way to go on one, unless you'd like to shell out the extra cash. Borg-Warner makes alot of good parts, your included. Any parts-plus store, napa, shucks/cragen/checker should be able to have one, or get one within a day or two. Good luck, Mark

 
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Discussion Starter · #4 ·
The knock sensor tells the computer when it is running too lean or the spark is too advanced. On an 85 Jeep you don't have computer controlled ignition, so I would assume it is for control of the stepper motor on the Carb. If you have by-passed the computer and disabled the stepper motor (the "Nutter" bypass) you don't need it. You should be able to find one at a good parts store, I found one for an 86 Astro for $34.00.

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Randy 80 CJ5
 
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Discussion Starter · #5 ·
The knock sensor is used on the later 4.2ls with feedback carbs to send a signal to the ECU when the engine is pinging. The ECU on these engines does have the ability to control the timing by retarding it under certain driving conditions. Pinging is one of these. If the sensor is disconnected, and the engine doesn't ping, no problem! If the sensor is making voltage under normal driving conditions (its a Piezo-electric voltage generator) the timing will be retarded causing lower performance. These sensors rarely give trouble though so you may be able to find one at your local self serve wrecker for a buck or two of of any AMC or Jeep from about '81-'90 with a computer controlled 4.2l. This sensor has 1 wire to it and has a red plastic insulator and is bolted to the intake in front of the carb. Hope this helps, good luck.

 
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Discussion Starter · #7 ·
Thanks, Rylan,
I posted this for a friend who has an 85 CJ. He already bought the sensor, and installed it this weekend.

Now all he has to do is replace the intake manifold! /wwwthreads_images/icons/frown.gif

Jon-YJ94
I6, 3.5" Black Diamond, MORE, & more
still working!
 
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