When you replaced the ECU from another vehicle did you replace the key responder and ignition too? Because 1996 and up need the key transponder, ignition module, and ECU to all match or to be reprogramed to work in another vehicle.This has been an on going issue for me for the past 3 months with my 99 Galant. I haven't had too much time to deal with it recently due to heavy schedule with work. Now that things are slowing down at the shop for us with SEMA this next week I would like to spend more time figuring out what the issue is.
I have checked all of the following items per the FSM troubleshooting information and I am still back to the MFI circuit for probable cause.
Compression is good in all 6 cylinders (average is 95)
Timing dead on (TDC checked with wooden dowel and bore scope, markings all lined up)
Spark to all 6 cylinders (New distributor, plugs, and wires have been tried)
Fuel Pump is working properly (has also been replaced to be sure)
Battery Voltage is steady at 12.43v
MFI Relay - Terminals 3/4 is 12.43v, continuity between terminals 2 and 4 is 71.4 Ohms, continuity between Terminals 1 and 3 with battery negative connected is 1.0 Ohm, open loop with the negative disconnected.
Replaced ECU (was pulled from a running vehicle)
Now here is where I get dragged back to the MFI system. When I am checking the injector connection terminals one has the supplied battery voltage from the MFI Relay (12.4v), and the other terminal is apprently suposed to have a flucutating signal (0-12v) from what I have been told. Checking this terminal however I am only seeing a 0.01-.02 voltage on all injectors while cranking. Reading the FSM MFI circuit diagrams I see the terminal with the fluctuating voltage is an "input" to the ECU. This leads me to think that the ECU does not distribute the voltage signal to the injector terminal, but the steady power voltage is supposed to "pulse" through the injector and in turn sending that voltage signal to the ECU.
I apologize for the "book" here, but I am seriously sitting at a dead end with the car currently. I have tried searching the FSM for weeks now trying to find information on the fluctuating injector signal voltage but have found nothing.
** Additional Note- The car was running for a good 20-30minutes at idle, rev/decel engine fine. It began to stumble on idle and killed out a couple times. It would start back up, however it was hard starting. As it sits currently the engine will crank over and there is noticeable signs of stumble starting but it will not completely fire up