[ bad ground location Interference caused by a bad secondary ignition coils ground. [wave form of the interference]

I got a very weird problem with this one, first up it came in for misfire and lack of power problems and it end up with a no start condition. I replaced one ignition coil and reconnect an intake duct. Then the car runs well but still has no power. Soon after it started stalling and running rough. 2B0B Throttle valve potentiometer and 2B06 throttle valve potentiometer 2 came out. I scoped the 2 signals and power/grounds of throttle body. At first it looks to me like a DME(control module) power feed or ground intermittent problem. I then realize that the spikes were occurring only when the engine was running. In fact, the spikes were noise. I then scoped the ground of the secondary coils circuit and I saw immediately the problem.

Vincent from Quebec

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