Engine noise, reduced idling speed

[KevinM]

Hi Team, I need some help / advice please. My +2 has been running like a sewing machine recently....but..yesterday whilst driving in slow moving traffic I noticed the cabin noise was louder at low revs, a very low frequency that was felt as much as heard, and also that the idling speed had dropped by 200rpm or so. This morning when I started her up the engine caught with a perceptible clunk that could be felt through the accelerator. I have noticed no loss of power but can't help thinking the symptoms sound expensive! Any thoughts?

Kevin

[richardcox_lotus]

Engine Mounting ?

[KevinM]

A good thought, although the engine seems as steady as it has always been but I will check, thanks.

Kevin

[paddy]

I had a similar problem with an engine mount where the car suddenly started vibrating a lot more, and the mount had just let the engine drop a bit so the airbox was sitting on the top of the footwell. If all engine or gearbox movements are being transmitted to the body, the startup "clunk" might be nothing more than the bendix disengaging awkwardly but it is now much more perceptible than before.

However, if there's also a drop in idle speed I'd suspect something else. Firstly, is it firing on all cylinders?

Paddy

[ppnelan]

I would check that the airbox &/or carbs have not come loose and are about to fall off...

Matthew

[KevinM]

Hi Paddy, I have checked the ignition and there is a drop in revs as I disconnect each plug so seems ok in that department.
Carbs / airbox seems ok Matt.....

[Carlos A]

Engine mount! It may look ok from the top. Take a look under... Carlos

[collins_dan]

How do the plugs look? It could be the temperature compensator on the carbs. If its been running well in the cold weather and now as it warms up, its not running as well, could be that or mix or carb leak... Dan

[Jason1]

Hi

A slight misfire would cause the revs to drop and then the engine would sound noisier; the top end tends to be noisier. Slight air leak?

Any idea where in the engine the noise is coming from? Top, bottom, front?

I once had a noisy alternator on a Ford Escort that sounded like the bottom end, the owner was convinced that the engine was a goner. The alternator bearings were hanging out. You really need to locate the noise and then isolate it.

Jason

[KevinM]

Thanks for all the suggestions so far....I have just started the car with the sump jacked up a little and the rumbling/clonk has gone so mountings are about to be ordered....! I am still a bit unsure about the running but as both issues arrived at the same time I guess they are somehow tied together, plug check next...thanks for the advice and I will keep you posted on the results.

Kevin

[davidfost]

I'm also in the engine mount lobby, having had something similar. With the engine idling, when you move the carbs lightly up and down the idle speed changes, ergo if the carbs are resting on the footwell top that would explain both issues. It's really nice when a seemingly terminal problem turns out to be cheap to fix....