I have a 96 3.8 with a problem. The car shakes when running. Thought it was the clutch, because it was starting to have trouble shifting. Replaced the clutch assembly and flywheel. Had the flywheel balanced and still have the shaking. Tried the harmonic balancer, still the same thing. Anything else that I should look into? Could it be the ECM? A few years back, the check engine light came on and the code said it was a bad CO sensor. I replaced both down side sensors, only to have the light come on several hours after the replacement. I have replaced them several times, even with Motorcraft ones and still have the light on. The mechanic at my local garage is also stumped. Thanks in advance.