I think i may have just experienced either valve-train noise/grinding or piston slap. I accidentally stepped on the throttle a mere 5 seconds after cold starting my 06' TL (5AT) and subsequently heard a loud grinding noise when the RPM's snapped up to about 2k and the noise ended right as the rev's dropped. Let the car warm up and it drove just fine after. Could it be something in the transmission possibly? My engine has always made a slightly audible ticking noise when idling hot which makes me think it could use a valve adjustment but it still sounded the same after the grinding noise, should I adjust the valves and check everything out or just forget about it? Thanks in advance.

 

Cold start? Assuming you are still in CA as your location states...it can't be that cold there to worry. Was your A/C or Defrost on? Adding throttle 5 seconds after you start the car should be nothing to worry about.

 

The ticking is more than likely valve noise. I also have an 06 5AT, sitting at 113k miles. It definitely needs a valve adjustment, but I just don't have the time to take the car down to perform the service. Not worth paying the price to have someone else do it for me either.

Not sure what the grinding may have been. My only real guess is MAYBE the starter had not disengaged fully yet and that's the grinding you heard. If the noise is a one time thing, then more than likely, it's not something you need to worry about, but just keep tabs on it and see if it gets worse.

 

Yeah by cold start i mean the first start of the day at around 70 degrees out, never use Ac or defrost before the car is warmed up. I always have recycle on if that is any help.