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FlyinEvo

Misfire at 5500 rpm and 250 kpa

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I have a customer's EVO 9 with a 2.4 4g64 block. It is misfiring at 250 kpa and 5700 rpm. All morotsports options turned off, plugs gaped to .022, tried different plugs as well as ignition coils. Raised and lowered ignition dwell, no change to misfire. It starts, idles, and drives fine, except for misfire under boost. I have also tested the injectors, and had the air fuel from 13.3 to 11.5 and no change. It seems to be hitting a load limit of sorts. It will rev to 8000 rpm without any issues without load. The scaling for the wideband seems to be off one full air fuel ratio point from the working dyno wideband. It's an old school AEM wideband gauge with a 5v out. None of the dropdown scales will read correctly. The dyno wideband was recently replaced, and we have tuned 1000+ whp cars on it without issue. We are also using the internal map sensor.

Log 2018-06-9 1;39;15 am.llg

EVO 9 2.4 idle 1.pclr

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I notice your Mivec is not working, Im not sure if thats your problem but it will be worth correcting.  Most likely you just need to turn on the pull-up resistor for DI1 and it will work.

For your wideband you can just use a custom calibration.  Set up like below should do it.

Have you confirmed fuel pressure is being maintained?  I see you still have the FP speed control set up.

There are no signs of trigger errors or limiters being applied by the ecu  in your log so if enabling the Mivec doesnot help the problem and fuel press looks ok then I would be looking closer at the ignition system.  Dwell is possibly excessive in your current map although I know you say you have tried less.

 

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I checked timing sync with a timing light and it's spot on. Fuel pressure is correctly rising 1 to 1, there is a Hobbs switch to activate the second fuel pump, and I have tried less fuel as well as more without any change to misfire with fueling changes verified on wideband. Is the Pull-Up resistor for DI1 on the board or in the software? I spoke to the customer and this issue was present with the previous motor as well as with the stock ECM. The injectors were tested and flowed, new wiring harness, proper grounds direct from battery to block as well as chassis, tried several ignition systems, new fuel pump and fuel lines. Only the crank and cam sensors remain the same, but I would assume it would show up in the log. Voltage is good as well. 

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Hello
I had such a block on a 2.4 motor, with the oscilloscope I checked the waveform of the crank sensor.
This waveform was deformed at around 5000 rpm and there was no error in the ECU.
I replaced the harmonica pulley with another and defect disappeared.
I think this is caused by vibration on the crankshaft of these 2.4L engines.
Augusto.
 

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12 hours ago, augusto said:

Hello
I had such a block on a 2.4 motor, with the oscilloscope I checked the waveform of the crank sensor.
This waveform was deformed at around 5000 rpm and there was no error in the ECU.
I replaced the harmonica pulley with another and defect disappeared.
I think this is caused by vibration on the crankshaft of these 2.4L engines.
Augusto.
 

You are right Augusto,  The same issue happened with a friend of mine , he was using Power FC with a 4g64.

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