Mechanics

ENGINE RATTLES AT LOW RPM

1995 Mitsubishi Diamante

Noises problem
1995 Mitsubishi Diamante 6 cyl Two Wheel Drive Automatic 130000 miles

I searched your archive but couldn't find an answer, so here's my question: A rattling noise comes from the engine when I turn the car on in Park. The noise increases when I shift to Drive, even when coasting without the accelerator down. With the accelerator gently pushed down in Drive-- between about 1,800rpm to about 2,600rmp--the noise gets very loud, but at any higher rpms the noise goes away. The noise is the worst first thing in the morning when I start it, and even though it gets less through out the day, it never goes away completely. I'd appreciate any ideas before I take it in to the mechanic. Thanks!
Avatar
Manfred08
March 2, 2008.



Is this a heavy metallic noise or a light tinny kind of rattle. Sounds like a heat sheild that loosened up by your description, which would be the latter symptom.

Hi Paul, thanks for the response.

It's definitely more heavy and metalic, almost gutteral. And I looked at the rpms more closely, and I have a correction to what I said in the original post: I hear the noise starting out in Park, just after I turn the car on; when I shift from Park to Neutral, the noise goes completely away; when I shift from Neutral to Drive, the noise comes back, and louder; when coasting in Drive, the noise is loud, as well as when the gas is down, BUT the noise goes completely away in Drive past exactly 1,100 rpm. (Not 1,800-2,600rpm I originally said).

I tried keeping the car in 1st gear to see if it was a gear problem (as opposed to when the rpms reached a certain point) and the noise still went away when I passed 1,100rpm in 1st gear.

Any thoughts? Thanks again for the advice.
Brian

Tiny
Manfred08
Mar 3, 2008.
Cracked flywheel maybe?

I think I would try to get it up in the air and rev it up to about 20-30 mph and poke around from the bottom.

Hi,

Just took the car in for a regular service check and had them listen to the noise. They said it was a loose belt in the air conditioning system and that it was something they'd seen before in the model. I never had the air conditioning running when I heard the noise, but they said even when the AC isn't turned on, the belt still spins and that was causing the rattling. They tightened the belt.

Anyway, I've only just driven it home but the noise is gone. I'll update if the noise comes back, but hopefully it's gone for good!

Brian

Tiny
Manfred08
Mar 4, 2008.