Random Misfire Check Engine Light
Jan 4, 2005, 06:38 AM
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Random Misfire Check Engine Light
I've just posted this in the Vishnu EXEDE forum so please excuse the double post.
My 05 evo 8 started stumbling occasionally in the last couple weeks and throwing the random misfire code with the check engine light. I’ve got 6,000 miles on the car and this hadn’t happened before. I searched the forum and read through most of the responses without conclusion and started looking at what I’d done different in the last couple weeks.
I have a mostly stock evo 8 with an EXED piggy back computer. I’ve been adding rows and columns to my exede maps and scaling every cell for low boost at low mass air flow and increasing boost, ignition retard, less fuel, with increasing mass air flow. The result of these complicated maps is very snappy throttle tip-in combined with heavy 3500 rpm torque at full throttle, and big top end.
Unfortunately it’s too much for the factory ECU / piggyback EXEDE combination. Even though the difference between cells was quite small, the fact they were all different required more brainpower than the factory ECU had. I’ve since gone completely the other direction and have only 3 or 4 columns of cells per map (5,10,100% MAF) and the top couple rows with the same values to establish the shape of the curves. Not only is the random misfire problem gone but the car runs smoother all the time. This and the research I’ve done about the myriad of conditions that can cause random misfire, leads me to believe the stock ECU needs more ram or better clock speed or increased cooling and a reflash from the factory isn’t going to solve the problem. I really think this is a hardware issue.
My 05 evo 8 started stumbling occasionally in the last couple weeks and throwing the random misfire code with the check engine light. I’ve got 6,000 miles on the car and this hadn’t happened before. I searched the forum and read through most of the responses without conclusion and started looking at what I’d done different in the last couple weeks.
I have a mostly stock evo 8 with an EXED piggy back computer. I’ve been adding rows and columns to my exede maps and scaling every cell for low boost at low mass air flow and increasing boost, ignition retard, less fuel, with increasing mass air flow. The result of these complicated maps is very snappy throttle tip-in combined with heavy 3500 rpm torque at full throttle, and big top end.
Unfortunately it’s too much for the factory ECU / piggyback EXEDE combination. Even though the difference between cells was quite small, the fact they were all different required more brainpower than the factory ECU had. I’ve since gone completely the other direction and have only 3 or 4 columns of cells per map (5,10,100% MAF) and the top couple rows with the same values to establish the shape of the curves. Not only is the random misfire problem gone but the car runs smoother all the time. This and the research I’ve done about the myriad of conditions that can cause random misfire, leads me to believe the stock ECU needs more ram or better clock speed or increased cooling and a reflash from the factory isn’t going to solve the problem. I really think this is a hardware issue.
