5 speed 2.3l....whenever the a'c is running (i guess bringing down the rpms?) and the clutch is out in nuetral, the engine will rattling pretty violently. When the clutch is pushed in it almost goes away immidiately. Since then the tranny was rebuilt, new clutch, new pilot bearing, and a new throw out bearing, yet the noise still remains. I drove the truck pretty rough and someone pointed me in the direction that it could be valve knock, and the only think the clutch pedal had to to with it was maybe putting the perfect amount of drag on the engine to produce that resonation of the engine. Has anyone had anything simliar to this?

Kyle

 

it could be the a/c compressor

 

I can get the rattling noise when revving the engine while its at its lowest idle point, its not as violent then as when the a/c is on, but i had the a/c condensor checked and he said that was not the source of the noise.

 

ive had the same problem with my 2.5 5speed since i got it. i think it is just the drag placed on an idleing engine and the drag with the clutch out is enough to drag it down a little further.

 

The unloaded gears in the Mazda manuals used in Rangers and F150s do rattle at an idle when the clutch is engaged. The fewer the cylinders, the worse the rattle is. That makes your 4-banger worst case. Loading the engine with the A/C at idle makes the engine shake that much more and increases the rattle.

If you get the opportunity, compare it to another truck with the same drivetrain and similar odometer. If they are the same, chances are it's the nature of the beast and you won't be able to improve it.