Ok, Here's a diagnostic and a how-to for V8 folks that have the following going on with their engines
- Happens on cold start
Sounds like a rod knock or bottom-end tapping noise when you put it in gear with your foot on the brake
You might not hear it when you're in neutral or park or driving along but when you strain the motor, there it is
Goes away after a few minutes and does not make the noise once warmed up. May not make the noise the rest of the day.
Hard to hear outside the car.
Sounds kind of like a piston-pump noisily pumping.
This is NOT
- A rod knock
An exhaust leak
After reading here, I saw someone had posted that they replaced their "Fuel Injection Pressure Damper" and that took care of their symptoms...
I did the same thing, and VIOLA! a quiet engine on start-up.
Joy!
It was reported that this part was $105 from the dealer. I got it with shipping included from RockAuto for $34. Part #430 FPD4.
It is located at the rear, top of the engine on the driver's side, right above the rearmost injector.
It takes a rag (to catch a little fuel), a 22mm open end wrench and about 10 min time to remove the old one and replace it with the new one.
Simply unscrew it, watch the little bit of fuel that comes out, take the washer off the old one and put it on the new one, screw in the new one, snug it up and job done.
Easy fix! and, at $34, this is MUCH cheaper than an exhaust manifold or a bottom-end engine rebuild. Might be worth trying before you go down a more expensive path to repair...
Here you can see the new one the engine
Here's the old one on the part box