Help! What controls the timing on a 90 560 SEL? How do I adjust it? Mine was at 30 degrees advance at 950 idle . It smoothly advances to ~40 degrees as the engine revs. Car runs fine and the emissions are all very low, passes smog, but the timing is too high. R16 sets timing with no vac on EZL. I changed it to get 0, but vac on, gets it back up to about 30.

I cleaned Idle control valve, removed andblocked the bypass at the ICV to get 850 idle and 20 degrees. I think this means too much gas. The ICV current is about 600ma. fairly open?

Adjusted mixture 1/2 turn CCW to get 650-700 idle, (in spec), but timing is still 12 with vac on. Its 0 tdc with vac off. duty cycle voltage is about 4.1VAC 70%? I put the 750 ohm R16 back in to get about 7 vac off 12 vac on.

X92 LED never flashes. LED comes on when button is pushed with engine running. engine off, ignition on LED on, button does nothing.

Any ideas?

Gary,
I would like to know also.
Good luck

The EZL determines timing based on RPM and load (vacuum signal).
At full load vacuum is near 0 to prevent pinging as you lift on the pedal vacuum will increase (timing will advance) for better economy.
The centrifugal advance in the distributor only affects the rotor and cap (advances rotor with speed) so the tip dosn't have to be 2" wide to handle the range of timing adjustment.
Mike

Thanks Mike and estimate, long story short. retrying X92 got it to work right, nebie I think. No errors and got used to reading ratio. Getting the ratio was tricky, I think because the EHA was a little too rich. to get 10% between idle and 2000, I had to go to about 60% on my dwell meter 4cyl scale. I think the meter reads low because when I drop rpm from 2000 to idle, % freezes for a second or two at 45%, exactly midscale on the dwell meter. The meter has different scales for 4,6,8 cyl, but 8cyl scale reads 1/2 of 4cyl: 30%. Any help anyone as to dwell reading to %?

Finally found a good thread on the EHA and found the current at +.35+-.1. Scarry business the first time. 1/8cw made it worse: %up to 70%. Then went 1/4ccw (and found it easy to loose track of where the little allen screw was)

This worked good and tried another 1/8 to find for sure I had over shot the right place and started the 1/8 steps back. Each time you have to readjust the idle and 2000rpm ratio to <10%. The common point moves as you adjust the EHA. Mine had a sweet spot when the EHA was finally at 0+-.1, the ratio at 2000 magically fell exactly in the middle of the idle ratio.

Is that a good clue of when the EHA should be adjusted? When you adjust the idle ratio to 50% and the 2000 ratio is different and outside of the range of the change at idle???

End result: success. The resulting idle came in at 600 to sometimes 650 and timing is about 15 (If I remember right, its been a few days) with vacuum. Its been cold here so I'll check this again when weather is better.