Rattle at exactly 2750rpm

[JMiller]

I get a rattle at exactly 2750rpm from the belt side of engine in any gear and neutral, belts and pulleys look good and timing belt and components were replaced maybe 15k miles ago. The sound started about a month after i installed my prothane mounts. It sounds almost like a rattle snake with a little bit of a metal on metal sound mixed in. It only does it at 2750rpm not before, not after. Any info to help the situation would be great, thanks.

 

[crash89]

More then likely you have a bolt loose and that 2750 is just the right "frequency" to make it rattle a bit.. You could start by just looking around for loose bolts in the engine bay and under the car..

 

[rlacasse1]

How about a loose exhaust heat shield?

 

[TunaTalon]

2700 is about the RPM that the second order harmonic vibration from missing or out of sync balance shafts resonate with the DSM chassis. The vibration is less noticeable below or above the resonate frequency. The Prothane mounts would cause the vibration to be more noticeable than OE Mounts.

However that just explains why at that RPM. What piece is rattling needs more looking and less theory.

 

[boostNmetal]

I've had a problem like your describing. The timing belt tensioner arm had a small divot worn in it. Its worth looking into.

 

[JMiller]

Alright,
Heat shield - I run FP mani no heat shield
Loose bolts - will check tomorrow.
Timing belt tensioner arm - will look at also
Anything else i should maybe check?

 

[drzdude]

I have the same vibe as well and I've checked every thing twice Its driving me crazy looking for it.

 

[rlacasse1]

Do you have any heat shields anywhere else on the exhaust?

Although, if you have an FP manifold, I would imagine you have a full exhaust under there as well.

 

[JMiller]

Yeah 3in SS, O2 housing to muffler. Check my mod list in my profile or my cardomain
http://www.cardomain.com/ride/2730581/1998-mitsubishi-eclipse