2004 Acura TL 6MT shakes violently 1200-2000 RPM

Hi everyone,
My 2004 Acura TL with 6 speed manual transmission has an issue. When the RPMs go between 1200 and 2000 the car shakes violently as if the engine isn’t attached or is trying to get away. At idle it’s silky smooth and after 2000 RPM it feels fine too. The gear I’m in doesn’t matter and this shaking happens whether I’m standing still or driving… it just happens in the 1200-2000 RPM range. Again, this is not a small amount of vibration, I’m talking about seriously shaking the whole car.

This is what I’ve done so far:

  1. Replaced the three engine mounts two days ago, and double checked the transmission mounts and they seem fine. At the same time my mechanic discovered a few bolts on the subframe that were loose, and we tightened those.
  2. Replaced O2 sensor that was causing check engine light and it’s fine now.
  3. Timing belt, clutch and power steering was done by previous owner maybe 3-4 months ago.

I’ve been looking wide and long for any ideas on what this could be… Hopefully someone here can provide me a hint or at least the beginning of a theory.


You’ve got either a fuel or ignition problem. Probably coils or spark plugs or plug wires but could have a fuel filter or pump not up to snuff. Might be worth the $100 diagnostic fee to get it on the computer and check out what’s happening. Otherwise its just guess work with no trouble codes.

A fuel or ignition problem that is fine at idle and all higher than 2000 rpm? Hard to think of one.

I will check the spark plugs tomorrow, but I feel that is the plugs were worn it should have an impact at higher RPMs as well.

I just sat in the car and turned it on and confirmed the problem again. Feels fine at idle around 700-800 RPM (some vibration, but not bad at all), and then as I give a little gas I can see the wheel, mirror and door (kept it open) shaking up, down and sideways. Worst of the vibration happens in the 1200-1600 range, and dissipates and pretty much goes away over 2000.

Could this have to do with the harmonic balancer? The timing belt job was done not too long ago, and perhaps the mechanic messed it up somehow and didn’t install it properly, or one of the parts that goes into the timing belt change?

I would suspect the harmonic balancer.