Wisconsin Joe

The wire for the belt tension warning light is zip tied to the spark plug wires?

So it's warning when the plug wires don't have enough tension on them? (They are, after all, "high tension" wires )

FredR

Someone did not like the ignition wiring route and no point in connecting the belt tension wire is there!

What is that round doobrey thing to the left of the filler cap?

Rgds

Fred

zekgb

That's the diagnostic plug for an S3, among other things it is used to measure idle mixture while setting it at the MAF.

SeanR

It's an 86.5 so the wires are routed correctly. The plug is a semi-diagnostic plug, can tell if you are getting idle/WOT from there. I've only used it with Porkens tool.

JPTL

That's the wire. The brass lug connector at the plunger had about 2mm of play in the groove.
As you confirmed Dave, there were several unknowns and a few known challenges to properly reinstalling the tensioner if I had opted to remove it by going in from under the car. I didn't want to risk a botched job.
Since I was in a time crunch, I opted to do a temporary fix:
I cut a notch out of a stainless washer so that it was like a C. With needle-nose pliers from below, I pressed it into the groove where the washer should have been. It's in there solidly. Buttoned things up and tested continuity at the thru-cover pin and got a solid ground. I'm pretty certain that the C washer will stay there for awhile. If it ever does come out, I'll know because I'll get the tension warning.
Thanks to all who took the time to post, research and help me troubleshoot this. You were all a huge help. Those of you who'll be at Frenzy, beers are on me. For those who won't, I'm sending some good Mojo your way

Bill Ball

How can the end on the tensioner plunger have so much play? Is the spring missing? If the washer was missing, the spring should still hold contact, in fact, at even a lower tension that spec, as the washer "preloads" the tensioner warning system with extra tension.

JPTL

The spring isn't missing. Without taking it out, I can't really tell why there was such a big gap. I had limited view of the plunger.

Bill Ball

I'd say it needs to be taken out then. Something is wrong with the assembly.

Mrmerlin

other thing that can happen is the isolator bushing on the piston pin can crumble,
and then the cylinder it fits into can get the crumbled plastic between the seating area ,
thus breaking the ground,
I have seen this a few times now best to have a new bushing on hand

Kevin in Atlanta

+1

Did this twice until I figured out was wrong.

JPTL

At the track today, driving the car hard and all is good (fingers crossed). Fixing this will be the next order of business.
Is there a detailed schematic anywhere that shows the bushing and washer?