Hi Will, aka Car Surgeon, as in Weird Al's spoof...

In Big Harry's thread on the 200 forum you asked me to put my two cents in on this. I try to stay out of stuff I don't know, and as much as some think 700s are like 240s, I will step ignorant into the differences every time.

For instance, the question about the ballast... I thought only turbos had those injector resistors. Well yours may indeed be a turbo. Just an example where I can't offer real experience. My turbos are k-jet 240s -- the ignition is ballasted, not the fuel injectors. :)

But what Amarin suggested is exactly what I think about this "missing injector pulse" red herring. Not that red herrings are not valid learning experiences, but lets consider putting the horse on the other side of the cause-and-effect cart: Your noid light quits because the car is in rapid decel. And, if you were to measure vacuum at the same time, I bet you'd see it drop too as the IAC tries to keep decel vacuum from sucking all the oil past the valve guides.

When I watch your video, or more importantly, listen to it, I think the fuel computer sees airflow cut off. I wonder why: Does it see a suddenly dropping AMM voltage, or does it see TPS closing. Try monitoring AMM voltage at the fuel ecu, which you can actually do with a multimeter. Check what happens at your noid light if you ground the TPS closed throttle contact while you have it running a couple thou rpm (throttle obviously open). Again, convenient at the fuel ecu plug.

Anyhow I have put a scope to 16 and 17 on EZ116K ICM outputs before -- 16, the one that drives the spark includes the dwell (width) information, and 17 is simply spark timing, which is enough to give the fuel computer what it needs to know about engine speed. I believe you won't see it disappear in sync with your noid light going black. It is 8 which tells the ICU what it needs to know about ignition advance from what the ECU learns from your AMM about engine load.

None of this is going to be conclusive to you without being able to see the timing and waveform. Maybe if your multimeter has a duty cycle function along with its frequency scale, and you get some experience from a correctly working system. That's what I was shooting for about 8 years ago, testing a few ICUs and ECUs in Mrs. B's 245 -- a baseline. I was following the oft heard advice to keep spares, especially AMMs and ECUs. Much cheaper at the junkyard before you really need one fast.


--
Art Benstein near Baltimore

First Guy (proudly): 'My wife's an angel!' Second Guy: 'You're lucky, mine's still alive.'