2010 CVPI

Ok, I am new to the forum and have read alot about the problem that I have with my "company" car. I have a knock type sound when I accelerate that is annoying as all get out. It sounds like it is coming from the undercarrige. I brought to a dealer and they are stumped. After drive shaft, drivers side cat, and both exhuasts changed they can not find the knock or rattle. I do not think it is a spark knock as that would come from the engine area I believe and no other "company" cars have it. We all get our gas from the same pump. They have checked the flexplate and are at a loss, any ideas?

Knocks are hard to find sometimes. Look for something caught on the edge of a tire, between the wheel and the brake mount, strings caught on the u-joint of the drive shaft, things like that.

I had a 1976 impala wagon that had an annoying knock / tap at about 55-75 MPH. The dealer actually told me to live with it. In 1980, I had some idiot side-swipe me on the driver side rear quarter panel. When we cut off the panel, Chevrolet workers had put 3 nuts on a nylon string and hung it inside the panel. The knock / tap I had was from that. I also found out that I had a wheel that wasn't exactly straight which was causing the slight shake (but not enough to notice) where the nuts tapped on metal. Chevrolet swore that none of their employees would do something like that. SURE!

i know that this mostly applies to older crown vics, but could it be a timing chain issue?