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Montero 3.5L DOHC misfire (6G74 engine)
Montero 3.5L DOHC misfire (6G74 engine)
Hello All!
My car suddenly lost 2 out of 6 cylinders. I hooked my oscilloscope to camshaft and crankshaft sensors, and the ECU output controlling the 3 coils (waste spark system). You can see that one of the ECU outputs is a flat line, while the other seems to be firing more frequent then needed. As if the ECU thinks it must fire the same coil two times in a row, instead of the correct one. I was wondering of you can advise me if the crank/cam signal looks good. Maybe there is something wrong with the sensors that makes the ECU think that it must fire the wrong cylinder?
Here is the reading:
Channel 1 should be crank sensor, channel 2 should be cam sensor. Channels 3,4 and 5 are ECU outputs controlling the 3 coils.
Or maybe the ECU needs replacing? Any advise would be helpful!
Thanks in advance!
My car suddenly lost 2 out of 6 cylinders. I hooked my oscilloscope to camshaft and crankshaft sensors, and the ECU output controlling the 3 coils (waste spark system). You can see that one of the ECU outputs is a flat line, while the other seems to be firing more frequent then needed. As if the ECU thinks it must fire the same coil two times in a row, instead of the correct one. I was wondering of you can advise me if the crank/cam signal looks good. Maybe there is something wrong with the sensors that makes the ECU think that it must fire the wrong cylinder?
Here is the reading:
Channel 1 should be crank sensor, channel 2 should be cam sensor. Channels 3,4 and 5 are ECU outputs controlling the 3 coils.
Or maybe the ECU needs replacing? Any advise would be helpful!
Thanks in advance!
Re: Montero 3.5L DOHC misfire (6G74 engine)
Actually, this morning when I started the car, all 6 cylinders worked. I managed to quickly capture the waveforms before the engine acted again.
I'm sorry the setup is a bit different now (I was in a hurry) - Channel 1 is cam sensor now, Channel 2 is crank sensor, and the rest of the channels are the coils. These below should be good waveforms of 3.5L 6g74 engine.
After I stopped the engine, and started it again, the misfires appeared again.
To my eye, the crank and cam sensors look fine in all cases, so sadly, the problem must be the ECU.
I've replaced the electroilytic capacitors in the ECU, cause I read on internet they go bad with time, but nothing changed. I'll try to resolder all ECU joints, but probably must replace the E310a IC as shown here:
https://youtu.be/SPW7tf_QjpQ?t=47
Weird enough, only 2 of the ignition control pins go to this IC. The third goes to another component.
If you have any ideas what outside of the ECU could be causing this problem, please feel free to share.
Thanks again!
I'm sorry the setup is a bit different now (I was in a hurry) - Channel 1 is cam sensor now, Channel 2 is crank sensor, and the rest of the channels are the coils. These below should be good waveforms of 3.5L 6g74 engine.
After I stopped the engine, and started it again, the misfires appeared again.
To my eye, the crank and cam sensors look fine in all cases, so sadly, the problem must be the ECU.
I've replaced the electroilytic capacitors in the ECU, cause I read on internet they go bad with time, but nothing changed. I'll try to resolder all ECU joints, but probably must replace the E310a IC as shown here:
https://youtu.be/SPW7tf_QjpQ?t=47
Weird enough, only 2 of the ignition control pins go to this IC. The third goes to another component.
If you have any ideas what outside of the ECU could be causing this problem, please feel free to share.
Thanks again!
Re: Montero 3.5L DOHC misfire (6G74 engine)
Hello,l have the same problem as you,l have the Pajero(6g74 3.5 v6) that works with two cylinders less and one of the outputs of the ecu has no signal. Even changing the ecu,the problem persiste. Were you able to solve your promlem? Many thanks in advance.
Re: Montero 3.5L DOHC misfire (6G74 engine)
Thank you so much!