Testing opti and icm while they are out?

[Aaron4TAMU]

Just wondering if there was a way to test the opti or icm after they have been removed (bench test). I'm working on a timing issue (2 years ago it abrupty started having issues with backfire/rough idle/dying, and haven't touched it since, till this week), have it torn down to the timing chain (wanted to do a tune-up while i'm in it). Mechanically the timing is fine, so now I have to diagnose the ignition side of it (I tried to use the shoebox guide for this, but I am almost clueless on the electrical side). I also used starter fluid in the intake, and it tried to fire off, which leads me to believe that the ICM is good (otherwise I would get no spark at all right?). I also noticed that the 4 pin connector that goes in the opti was pretty banged up (the base was completely smashed). Any comments or suggestions are greatly appreciated.

[Injuneer]

The optical sensor in the Opti provides the cam position, so the PCM can time the injectors and the spark. If the two pulse signals that come from the Opti are intermittent or incomplete, you will have problems with erratic timing, or the PCM will shut down the fuel system. A damaged 4-pin harness connector, corrosion on the pins, or even missing locking clip tabs can cause these problems.

If you can supply 12V to pin C of the Opti connector, and a ground to pin D, as you slowly rotate the Opti drive, you should see a 0-5V square wave on pin A and pin B when measured to ground. This would confirm the optical module is working, and the signals are getting to the harness connector. The high resolution pulse (pin B) is 360 pulses per revolution, the low res pulse (pin A) is 8 variable length pulses per revolution.

See Shoebox's Opti wiring diagram:

http://shbox.com/1/95_ign_system_schematic.jpg

An auto parts store can test your IC Module. One problem is that the ICM issues can be caused by heat soak from the engine head, and the ICM isn't going to be hot when an auto parts store tests it. Heat soak can also affect the Opti optical module.

[Aaron4TAMU]

Thanks for all the info again Injuneer! I don't think it would be a heat soak issue, because it does the same thing from a cold start. I'll take the ICM in to have it tested...as for the opti, I'll get someone over here that knows more about electrical to help me out with your advice. That 4 pin connector is in bad shape, would I have to remove the harness to swap it out, or is there an easier way to replace it? I also noticed that the wires are badly scarred right where they enter the seal, should I just cut them and resplice?

[Aaron4TAMU]

Update:

Got the ICM checked out...it's good. Went to all the wreck yards in town to try and find an opti harness, no luck. So I'm going to order a new one online here: http://www.bmotorsports.com/shop/pro...roducts_id/913 . Didn't want to wait for shipping but oh well. As for the opti, I found a local shop here called GW Customs, owned by Greg Wilson (this guy seems to run a nice shop in the College Station area if anyone is close by). Took the opti to him, and he was going to run the tests on it, but we need that connector with pigtail because of how deep those terminals are. I will most likely go ahead and replace that opti since I'm in there, but I would like to know if that's my problem or not before I start throwing everything back together. Thanks again for the help!