Sorry to post here, I figure the CL is a mechanical twin of the Accord. Just picked one up for my gf, has 91K miles and I'm not sure what to make of this.

Car stopped, engine running, trans in neutral and clutch engaged - fine

Once I depress the pedal and disengage thte clutch the RPM will drop and the engine will want to stall. It also makes a clunking noise.

If I put it in 1st gear and roll away, it'll do it, but make a clunking noise. Clunking noise doesn't exist if I rev the motor in neutral, clutch engaged.

Not sure if this is just a simple throw out bearing or a crank issue? Thanks.

 

take to tranny shop, normally the diagnosis for free. or will know if its the clutch or not.

 

I would guess that since the engine shows low RPM and has a clunking noise when the clutch is disengaged, then the transmission is not the problem.

Maybe when you engage the clutch and the transmission is in neutral, it stabilizes your crankshaft, making the clunk go away, allowing the RPMs to reach where they should. When you put the car in 1st and try to drive, it is requiring the engine to work a lot more than when the transmission is just in neutral, so the clunk (and lower RPMs) come back.

I would guess something is wrong with your crankshaft, like you thought, but I'm really not sure.