Taking a break from wrenching.

Looks like I had/have multiple contributing issues going on.

1. Bad ECU
2. Idle position switch not adjusted right
3. Timing.
4. Something else?

As I was exiting the parking structure at work yesterday, my ECU died. Coasted into open parking spot and noticed the telltale fishy smell. While waiting for a kind coworker to give me a ride to pick up my spare ECU I searched +idle +ECU and found a few cases of ECU's going bad causing idling issues. Great, I thought at least the cause is found.

Not so fast. Checked new ISC coils and they are still in spec at 40ohms. When I installed my spare ECU, the idle was back up to 1800 cold or hot. Found that the idle position switch at pedal release position was open. Adjusted the TPS according to the FSM, and verified that the switch was closed (continuity) with the throttle lever touching the fixed SAS, and open (no continuity) when the throttle lever is opened a bit.

Idle seemed to operate more normally, with an exception. 1800 at first startup with the engine cold, then after a minute the idle bounced around for awhile, down to 1300, up to 1700, repeat, repeat, repeat, until it warmed up more, then dropping down to a steady 1000. Flaky fast idle air valve?

Did the curb idle speed check. Found my timing with the timing terminal grounded was 0?BTDC. Adjusted timing to 5?BTDC. Removed the ground from the timing terminal and the actual timing jumped to 23?BTDC instead of the expected 15?BTDC. I didn't check actual timing prior to adjusting the distributor. Idled at 1500rpm.

Adjusted the timing to 3?BTDC with the timing terminal grounded (right on the edge of the spec) and the actual timing with the ground removed is 18-15?BTDC and 1200rpm idle.

That seemed close enough to try adjusting the basic idle speed. Grounded the timing terminal, and grounded pin 10 of the self-diagnosis connector. Found that the speed adjusting screw on the throttle body was already all the way in, so I can't get the idle any lower than 1200.

Next, I'll replace the throttle body.

Any concerns about the way I set the timing?

1990 Monty LS 3.0 A/T LWB. KYB front shocks, OME rears and coils. 33x10.5 BFG Muds. 5.29, 2.85, RD110, RD46. 2 bouncys. Aisins. Monte Disco swaybar disconnects. GenII t-arms, idler arm, UCA's, V45W front brakes. 2in BL.