Another tac question

Does anyone out there know what it could mean when the tack blips up to about 500 rpm when starting and also when shutting down? It doesn’t register anything while the engine is running. There is this little guy

That I Think is a ground wire for one of the two suppression filters and shouldn’t have anything to do with the tac. Theres no change in symptoms when grounded.

Update;Not that many of you will care if the tachometer works or not, but I went through the troubleshooting steps in the manual and it appears the tach itself is bad. Now the procedure for doing those tests and replacing the tach describe doing so by removing the fuse pannel and the air intake tube. Needless to say that’s a pain. I found it was much easier to remove the left defrost vent and reach in behind the speedo. Pretty easy to remove the speedo and then the tach. A mirror may help to identify what you’re touching but it’s pretty straightforward, much more so than trying to get at the backside from the hood.