I was talking to the Dealer where I bought my CX-7, wondering about the knocking in the engine. They did some research on specs of the engine and found out the the reason the engine is loud while idling is because of the fuel injectors. Most cars fuel injectors run about 50-70 PSI and the CX-7 runs around 1,000 PSI (I think he said a little over 1000psi). So if anyone was wondering, there you go. I did notice that if you run Shell or BP gas my CX-7 seems to run quieter and has a little more power (premium octane).

 

Just bought a 07 CX-7 with 16k on for the wife. She loves it. Anyway, I was real concerned with the noise when we test drove it. Here is a nice link on the car and Engine.

http://consumerguideauto.howstuffwor...a-cx-7-cga.htm

 

With electric/electronic fuel injectors it often proves advantagous to provide more than one ground return path for the injectors. Often there is a single heavy duty ground strap from the engine, top/center/rear of the intake manifold, to the firewall. If you add a second ground strap,HEAVY ground strap, from the engine blockdirectly to the battery that will sometimes reduce the noise from the flexing of the firewall surface due to the HIGH injector inrush current flow.