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Old 02-14-2010, 07:59 PM   #1
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Default cant go turbo until this is fixed help

i tried posting this at but no one is helping out?
I'm trying to help a friend diagnose his no start issue on his 92 1.6L and I am leaning towards a bad PCM. I have read the No-start troubleshooting thread and the only thing I haven't checked is having power at the "X" terminal on the ecu. I have no idea which pin it is as I don't have access to a factory service manual or enthusiast manual unless I missed an online version. If I did, direct me in the right direct please! lol. Anyway, here is the rundown on what the car is doing and what I have done so far in my attempts to resolve the issue. Let me know what you guys think. In short, the injectors don't seem to be firing.

-Fuel pressure is around 40psi while cranking so the pump is working(Confirmed via inline gauge)
-All 4 spark plugs are firing (The car will attempt to start when given some starting fluid)
-Compression checks out
-Fuel Inj relay is working (I removed the cover and watched it operate correctly and even activated it by hand) I also noticed that the IACV clicks when the relay engages. Is that normal?
-I am getting no pulse on the injectors (Confirmed via noids/test light)
-CEL showed code 3
-I pulled the PCM and visually inspected it, but did not find any definitive burn marks. I assume there could still be an internal malfunction?

So as you can see, it appears I have narrowed it down to the PCM unless there is something else that controls/influences the injectors??? The IACV I believe is also acting up as the car idled at 1000rpm before it stopped running altogether. Could a bad IACV kill the PCM or inhibit starts? I come from working on mitsubishi's and on some cars a bad IACV can kill the PCM. Is that something to worry about in the miata circuitry? I'd hate to try another ecu only to kill it. Thanks for the help!
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Old 02-14-2010, 08:18 PM   #2
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The fact that your CEL is actually giving you codes makes me want to beleive that the computer is fine.
You might want to tell everyone what a "code 3" is.

EDIT: Here is your ecu pin diagram if you really want to test voltages.

If by code 3 you mean G signal, swap your CAS with a known working one and see if it starts.
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Old 02-14-2010, 08:26 PM   #3
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Code 3 is problem with CAS signal. There is either a problem with the CAS wiring, or the CAS itself is dead.

No CAS = No fuel
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Old 02-14-2010, 08:46 PM   #4
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Doesn't the CAS also control the spark events? Spark is fine. Are they on separate signals or something? Guess we'll grab a CAS and try it.
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Old 02-14-2010, 08:55 PM   #5
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Not sure on the specifics but theres a G signal and some other signal (I forgot the name). It could be that one controls fuel and one controls ign, I couldn't tell you.
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