MSefi.com read only forum (Jan.15,2018)

Iv searched the forums and i still cant find a solution. I am attempting to get my 89 Jeep YJ running using Megasquirt II V3 running V2.88 Code . My problem is that the IAC stops working after a couple of seconds. When I power up Megasquirt (key to run position) the IAC retracts and then extends (zeros itself) like it should but then will not move with the temp change when the engine is warming up. If I restart Megasquirt again the stepper motor will not move/zero. I have to wait at least 30 seconds before powering Megasquirt and then the IAC will usually move/zero again. When I am able to get the IAC to zero, if I immediately change the idle steps it will move to where ever I set it and then after a couple of seconds of not moving it, it wont move again unless Megasquirt is turned off for about 30 seconds. Even with a cold engine and the IAC removed if i power Megasquirt and the IAC moves/zeros and then restart Megasquirt right away it will not move/zero a second time.

Here are some of the things I have tried and checked so far:
- Wearing an anti-static wrist strap i felt for hot chips after leaving megasquirt on for 10-15min with the IAC hooked up.
- My first Thought was stepper motor was bad so i tried one from a working car and it did not help. I checked the coils resistances (about 50 Ohms each) no continuity between coils.
- Then I tried jumping the two resistors on the bottom of the Daughter Card. Thinking the over current circuit was turning on. that did not make any difference.
- I checked that all jumpers were correct and that my wiring and boards had continuity all the way back to the Stepper Chip. From where the wires plug into the IAC to the stepper chip pins (14,17,20,23) there was about .1 to .2 Ohms. Is this to High?
- Checked for shorts.
- And finally I replaced the Stepper Chip. (surface mount is not fun) and it is still doing the same thing.
-Tonight I am going to reflash Megasquirt and if that doesn't help try an older version.

Any one think of any thing else i could do? Before i buy a new Daughter Card and/or a different model stepper motor. I wish i had an Oscilloscope.

Thanks,
Neil

One other thing i just remembered. Before and now after i jumpered R5 and R6 on the bottom of the Daughter Card. There was 0 Ohms between the two resistors. That doesn't seem right? Does it? i did not jumper the resistors together but separately.

Thanks,
Neil