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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8606
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi 3000GT: Hey Doug I have a 92 3000gt car acting

Customer Question

Hey Doug I have a 92 3000gt car acting up and driving me crazy I am getting intermittent power to the fuel pump relay when this happens the idle drops and it stalls if I hold it at a high idle it will say running
Submitted: 2 years ago.
Category: Mitsubishi
Expert:  Doug replied 2 years ago.
Hi,
Before doing anything else, if you can get your CAS signal off the engine on a lab scope and see what it is doing, if the signal is getting jagged or cutting out etc.
The CAS sends the signal to the ECU for engine rotation which is what makes the fuel pump run... the ECU uses this signal to ground the MFI relay (fuel pump side) and power the pump. The rest of the system is just wiring.... so anything beyond those parts would be damage to the wires which of course would not be any fun to find, but also would not likely change with engine RPM.
The CAS signal -would- change with engine RPM and possibly clear up the issue, as would the ECU operation.
If you don't see anything unusual on the CAS waveform signal, or are unable to test it/replaced it anyway/whatever, then I would pull the ECU out and check it for leaking capacitors as is very common on the 91-94 models.
Given the engine speed changing the condition, the pump and MFI/pump relay being new, I would say it is most likely to be an issue with the CAS sensor/