Knocking sound from engine comparent

[Cumby]

Recently I have been noticing a knocking noise on my V8 4x4. I hear it on cold mornings when it's warming up and when I first shift into reverse. After it warms up it doesn't seem noticeable. Wondering if this is something in the front drive train and needs to be checked out?

 

[NuclearN8]

Exhaust manifold

 

[Cumby]

That's what I thought at first, but why would it only get noticeable when I put it in gear?

 

[fdbyrne]

The engine RPMs drop when you shift into gear. It's possible that in park the engine is spinning so fast that you can't hear individual knocks. Only when they slow down can you hear them individually.

 

[Cumby]

I've recently had a drop in gas mileage too. Wonder if that could somehow be related.

 

[progress4m]

If you can hear it only inside, but not outside, it only last under 1-3 minutes until engine is slightly warm (considering that starting ambient temp is around freezing) and it goes away with slight increase or RPM ( under 200 RPM increase) then what you hear is power pulses in the fuel line that do sound like a knock; there are some threads here about it…

Some have changed fuel dampener to illuminate this, some had dealer replace the fuel dampener and fuel pump;

The good part it is not the engine or anything serious at all… just can be annoying if it happens often;

 

[KBToys]

Mine does it too, after reading this post i figured its the same thing

http://www.toyota-4runner.org/4th-gen-t4rs/140692-v8-knock-cold-start-try-$34-fix-first.html