2004 TSX 5 speed auto. I first replaced all of my motor mounts since they were all broken, and this improved the problem some, however I used aftermarkets from eBay that were incredibly cheap. It has 220k so I replaced the timing chain and balance shaft chain, and their tensioners, as this had cleared up a vibration problem on my 03 k24 accord. Sadly this did not resolve it, so I proceeded to replace the plugs, remove and inspect the MAP sensor, clean the throttle body, change the trans fluid 3 times (I once read a post suggesting the torque converter can cause this), and finally I vacuum tested the front vacuum operated motor mount which I had just replaced, and it wouldn’t hold a vacuum. I capped off the vacuum control solenoid so that there would no longer be a vacuum leak there (I thought perhaps the unmetered air was throwing the A/F ratio off far enough cause the shaking) but again, no improvement. Does anyone have experience with aftermarket vs OEM Acura front motor mounts performing differently? And this is a severe vibration with no engine codes. The steering wheel bounces, basically the whole front of the car bounces hard. I’ve read many posts across the web on this but none that documented an accurate diagnosis and the subsequent solution.

 

Wow. You did just about everything. How's the mileage and power? Any codes popping up? Misfires or bad valves could cause that but you'd have a CEL in that case. Any funny smells from the exhaust? Oil or coolant consumption?