Скачать или смотреть 1986 vanagon tach problems

I have been working on a 1986 vanagon GL i purchased recently and most of the info i have been able to find here or elsewhere but i am having a problem with either my tachometer or the idle control unit.

When the van is at idle, my tachometer is bouncing all over the place but the engine does not rev along with it. So the engine stays at normal idle but the tach will not sit still.

I have checked and adjusted the throttle valve and it seems to be working fine. I have seen a few things about the transistor inside of the ICU going bad and mine is a little burnt but doesn't seem too trashed, i bought a replacement since it was cheap but i don't want to mess with the intricacies of that if not necessary.

I will post a photo of my tach after warm start where engine is at idle but not represented by the tach. please let me know of any other tricks i can try or things i should test before trying the new transistor. feel free to PM or reply with any additional questions if needed.