Craig --

One important aspect of adjusting the throttle on the early electronic FI systems is to be sure the throttle switch does not act as the mechanical stop. So you need to adjust the throttle (mechanical) idle position with a set screw, then adjust (rotate) the throttle switch so there is still a bit of rotational freedom.

As I recall (and it has been a while since I looked under the hood of my ES's -- like 15 years), the switch has a series of "zig-zags" that a wiper slides across as you open throttle. The computer counts the "make-breaks", and infers throttle position. There's also a contact closure that tells the computer when you've returned to idle position.

It's important that the switch not be the mechanical stop AND that the idle contacts still close. It's a delicate adjustment.

A good way to clean the "zig-zag" printed circuit in the throttle switch is with a pencil eraser. --
Re: Throttle Body Service[140-160/73] posted by Chris Mullet on
Friday, 30 October 1998, at 11:29 a.m.

According to Haynes, it appears the only "tool" you need is an ohmmeter. I'll bet a cold one that all lot of them get adjusted using the eyeball method - that is, leaving the cover off while rotating the switch and throttle plate, and watching for the the idle circuit contact to make and break at the right instant. At least I know a couple that have gotten adjusted that way, but I'm not going to admit who's they were. (There might be some high tech tech individuals on this board.)

Also, in the name of cheapness, if cleaning the contacts still leaves dead spots (characterized by short and sudden power losses while cruising) the contact fingers can be tweaked slightly with needle nose pliers to make them "track" across fresh spots on the printed board. --
Chris