How To: Removing the anti-tamper plug covering the mixture adjustment screw

[rdarlington]

Blatantly copied from this site: http://www.cabby-info.com/cis.htm#Plug

I'm copying it here because finding this info took me a month of research.



It’s very possible that your air/fuel mixture adjustment hole still has its anti-tamper plug installed. If so, it will need to be removed, or tampered with, in order to adjust the air/fuel mixture as described in the measuring and adjustment section.

The following tampering instructions are courtesy of tolusina of VWvortex.com:

“The easiest way to [remove the anti-tamper plug] is to flip the complete sensor plate assembly over and punch the plug out with a long thin punch.

The other tamper method requires drilling a centered hole in the plug, screwing in a sheet metal screw and pulling the screw up. You've got to be sure in advance that the drill bit used is small enough that the sheet metal screw you choose will have plenty to grip. Also, grind the point off the tip of the sheet metal screw so it doesn't bottom out.
Oh, yeah; you can't drill all the way through the aluminum plug [because] there's a floating steel disc in the bottom of the plug that will just spin when the drill bit hits it. The steel disc is to prevent drill chips from dropping inside. The steel disc is also what a pointed sheet metal screw will bottom out on before the rest of the screw gets a good grip.

If you booger things up with a drill and sheet metal screw, no worries; flip the assembly and punch it out, bottom-up.”

[Gumby]

Hmmm mine has the spring steel sheet on the top of the hole try to drill that out.. Have tried taking it to a machine shop and spring steel is the toughest.. So still there..

[Nicholas R]

Hmmm mine has the spring steel sheet on the top of the hole try to drill that out.. Have tried taking it to a machine shop and spring steel is the toughest.. So still there..

If you've removed the mixture unit from the car, then you might as well just split the housing. It takes maybe 20 minutes to get the unit disassembled to the point that you can just pop the plug out from the underside using a punch. No need to worry about drilling, chips, the drill slipping and cutting up the aluminum housing, or anything like that.