staplebus

Hi all. I’m currently hunting down an intermittent misfire and bucking that just started. I decided to pull out my reference sensors to check them. I noticed the speed sensor had a washer/shim underneath it and the other sensor did not... Has anyone heard of this? Should they both have an equal gap or is there a reason who on sensor would be shimmed and the other not? thanks

lee101315

Yes thats normal

staplebus

alright thanks a lot!

onspeed

Odd... When I did my clutch job, I was told by some people here that they were both supposed to have a washer. So I went and bought one from Porsche cause I assume I lost it.

staplebus

huh... does anyone else have any input. im going to order new sensors asap but may need one more...
lee101315 or anyone else, can you explain why only one spacer? onspeed, what did they say about two spacers... thanks!

Rogue_Ant

It only needs one spacer. One sensor reads a set-screw, once per revolution. The other sensor reads the flywheel starter-ring teeth. These are different "heights" on the flywheel, so accordingly, the sensors need to be spaced differently.

-Rogue

Mike Lindsey

One has a washer (2mm) (Rear Sensor). The washer emulates the thickness of the ring or lip (2mm) at the top of the metal tube (shield) that the other sensor (Forward/Flywheel) slides in putting them at the same height in the bracket. The tube is for starter wire intererence intruduced because the early 944s would misfire when cranking. It would't really matter if you had two stacked up, as long as you got your gaps correct. Early sensor brackets didn't use a tube or washer.

onspeed

I was told by someone on here that both of the sensors should have a spacer. Apparently I was misinformed, but I haven't encountered any problems with both sensors being seated ontop the washer.

My bracket is the older style I think, '86 car, I'm not sure if that makes any differences. But it doesn't have any tube. If it didn't originally come with a washer, then I just increased the sensor gap by 2mm from stock...

staplebus

alright got it, spacer on the rear sensor. thanks everybody!

onspeed

Could someone confirm that an '86 951 is only supposed to have a spacer/shim/washer on the sensor closest to the firewall? I put a washer on both, assuming they both had one, and I'm thinking about removing it to see if it's the cause of my car running rich. Just don't want to end up with a broken sensor and copper crap in my bell housing...

Mike Lindsey

We already did. The washer is there on the one because the other sensor has a sleeve.

Ronin-951

Now check your O2 sensor.