'02 3400 7X crankshaft sensor info

[Bridgetown]

I'm trying to diagnose a no start issue on my 3400 Fiero.
What should the resistance reading be on the 7x crankshaft sensor be?
(Mine is 950 ohms)
Also, should the 7x CKP sensor amperage fluctuate during cranking or hold steady?
(Mine holds steady at 0.06 vac)

[neophile_17]

I found battery voltage to be pretty important to the crank sensor. If I remember correctly the faster the crank turns the stronger the signal. Sooo, if like I was, you're trying to start an engine swap on a used sensor with a front mount battery that is at the end of it's life you're in for some frustration. The easiest way to check if this is your problem is... hook up a laptop to the aldl port and see if the computer is getting a non-zero rpm from the module. Good luck! A JY 3400 has been an awesome motor for our road race Fiero.

Sam

[robertisaar]

950 ohms sounds in the correct range, but the .06 volts during cranking? that seems incredibly low.

[Bridgetown]

Sorry, I meant .6vac

[Bridgetown]

Well, I replaced the ICM and the car started and ran good. Figured I had the problem fixed. As soon as I got the car up over 3k rpm it would stumble bad. I was right beside the parts store so I got new coils. Put them on right there in the parking lot, and the car run much smoother. Drove around for a while. Then I gave it full throttle and it is missing and stumbling bad, but only at Wot now. Any ideas what I should check?


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[caffeine]

All the wiring to the ICM check out?

[1988GTU]

bad spark plugs/gap-wires? Fuel pressure stable and accurate?

[Superdave]

Is the cps sensor wire spliced at all?

980ohms is spec, 950 should be fine. Might be worth it to swap with a new one just for troubleshooting.

[Bridgetown]

I was cranking the car a lot during trouble shooting, could that have fouled the plugs? I'll double check fuel pressure, it was good before the car ran during troubleshooting. I'll recheck now that it's running



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[Bridgetown]

Is the cps sensor wire spliced at all?

Crank pos sensor wire has not been spliced.


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[Bridgetown]

Just to clarify, the 24x crank sensor is not used by the ignition system during wot, correct?


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[Guest]

The 24x sensor is not used by the ignition system at all.

[Bridgetown]

Oh, really? For the SFI injection then?


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[Bridgetown]

I inspected all the wiring and fount that the wires to the CKP sensor was damaged, and barely hanging on. Replaced the wiring, didn't get a chance to drive it, but there was no missfire during free revving full throttle. I'll take it out tonight and see how it runs.


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[Guest]

Yes, the 24x sensor is used by the PCM, AFAIK entirely for the fuel side of things, though I'm sure it could easily be coded to be a look up for timing control as well, but I have not seen any indication of this.

The ICM uses the 7x sensor for RPM input directly, the 24x sensor and cam sensor are connected to the PCM directly.

Yes, fraid wires can cause headaches. Glad you found it.