1979-1993 & 94 Conv [Subscribe to Daily Digest] |
The knock sensor itself is really pretty stupid. It either works or is dead.
There are three things about the know sensor that may be at fault:
1- the sensor connection needs to be clean. I remove my sensor(s) and using a 400 or so grit paper do a figure eight on the metal contact of the sensor to clean it. I also take a piece of 3m scotch brite and put on the bottom of a long 3/8" extention and clean the contact point on the block.
2- the sensor needs to be point towards the left headlight. techincally 20 degrees off centerline, but the headlight is what the saab guys use. the contact surface has some interference (when you see it you will understand) that prevents you from pointing at the licence plate. If you have been having issues with movement use BLUE loctite. Just a couple of drops, really!
3- the connection to the sensor. this is the one I found having a problem most! it's only a two connection connector, but I've seen the receiving connector in the plug push out into the boot! Had to pull the connector out of the shell, bend the tang on the connector out (it's like a barb that is supposed to prevent the contact from getting pushed out when mating the two halves - aka plugging it in...) and push back into the shell. I had to work at my last one awhile, eventually put a little high temp RTV form a gasket in, let it harden, and then plugged back in. And all is good in boost land again.
BTW - your test of boost and then hitting the brake pedal shows that the switch for the cruise control cut out is functioning. If that switch is not working, ie never gets closed (they are constant on, get open when the piston is unloaded when you hit the brake or clutch) then the boost computer thinks you've hit the brake or hit the clutch and not boost. It does the same thing for cruise control, computer thinks you hit the brake or clutch to come out of cruise control. Good sleuthing!
I bet on the contact in the knock sensor backing out of the shell. They get tired with age and heat!
, Sat, 30 Sep 2006 06:32:17
, Thu, 28 Sep 2006 12:32:20
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