Help Troubleshooting a 3000gt VR4

Discussion in 'The BS Topic' started by Powers76, Jun 22, 2012.

  1. Powers76

    Powers76 Veteran Member

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    This vehicle is one of the best and worst vehicles I have ever seen. On the up side, its a gorgeous vehicle, twin turbo V6, AWD, All wheel steering, Active Aero, all the makings for an excellent racer. The downside however..... it is a massive pain in the ass to work on and absurdly expensive!

    Now, its not my vehicle but my friend has had it for many years and it has been a hassle almost the whole time. The most current issue that's been laughing at our attempts to fix it for what seems like a year is that when you put it in gear and start to drive it sputters violently. When its in neutral you can rev it up fine but once you start moving all hell breaks loose, it is not driveable.

    Things we have tried: Checked plugs, wires, vacuum lines, turbo piping
    Replaced fuel filter and pump, cat delete and downpipes (I think)

    What we know: He took it to a backyard mechanic who had a obd2 scanner or something and he said it was throwing a TPS sensor code and an O2 sensor code. The mechanic said he tested the voltage to the tps and said it was fine.

    Yesterday we tried to fix it again, we tried swapping ecu's from his old engine to this one but the vehicle wouldnt even start. We swapped TPS from old engine to new one but that didnt solve anything. After swapping the TPS I noticed that one of his O2 sensors was disconnected, plugged it back in and it made no difference.

    So sounds like it might be an O2 sensor but I just cant see the car running that terribly over an O2 sensor but then again I dont know much about those new cars. Any suggestions would be great! Thanks everyone
     
  2. harbone66

    harbone66 Veteran Member Lifetime Gold Member

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    They were great cars when they came out but the electrical glitch's turn them all into shiny turds! Were that part numbers on the ECU's the same? That unplugged O2 will make it run like crap. Did you check the coils to make sure none of them are shorting out, its kind of a notorious issue cause they dont act up unless they are under load. If there is a Mitsubishi dealer anywhere near you I recommend at least having them pull codes and run diagnostics with their MDS, thats the correct scanner for that vehicle. The aftermarket scanners cant get all the correct info out of those cars.
     
  3. Powers76

    Powers76 Veteran Member

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    Numbers on the ECUs werent the same. I just assumed it would work because the ECU hes using now is from his old engine. He blew the original and had one shipped over from japan which had the ECU we tried using. How do I check a coil, voltmeter? As far as the O2 sensor connection, ya we thought it was weird because it ran the same as it did with it unplugged as it did plugged in lol.
     
  4. harbone66

    harbone66 Veteran Member Lifetime Gold Member

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    it wasnt really the coil itself that went bad but the boot that is attached to it that goes down to the spark plug. pull them out one by one and see if you can see any burn marks on the boot itself. when they go bad they will arc out to the valve cover and cause it to miss horribly under load.
     
  5. Joekool

    Joekool Veteran Member

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    If the ignition system checks out fine I would look at the MAF sensor and the intake tubes going to the intake after the MAF. Sadly Ive had to work on a 3000gt twin turbo AWD in the past, one problem it had was the intake tube at the throttle body was installed incorrectly and the bottom was open (it had a metal tube with a rubber collar that sealed to the throttle body and had the clamp around it), under engine torque the tube would move just enough to suck air in, the engine would run like crap and stall. Revving in neutral and under light loads it ran fine though.
     
  6. Powers76

    Powers76 Veteran Member

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    Good stuff. Ill let him know.
     

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