Lotus Elan

Nasty noise

PostPost by: Roy Gillett » Fri Sep 22, 2006 3:28 pm

I know these things are realy difficult to diagnose by description, but can anyone help.

I was driving my +2 S130 today and suddenly when it settled to tickover at a set of traffic lights, it sounded realy rough and coarse as though the engine was shaking about. As soon as the engine revs mount off tickover, it is just as sweet as it has ever been, but as it settles to tickover it sounds dreadful. Tickover has also risen by about 400 rpm but even when I knock that back it still sounds rough. On opening the bonnet the engine is not shaking any more than normal (though from inside it sounds like it is) and all the HT leads are in position and removing each in turn has the same effect for each cylinder.

Performance doesn't seem to be affected and once revving it sounds normal and smooth.

What is going on?

Roy
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PostPost by: types26/36 » Fri Sep 22, 2006 4:35 pm

Roy Gillett wrote:I was driving my +2 S130 today and suddenly when it settled to tickover at a set of traffic lights, it sounded realy rough and coarse as though the engine was shaking about. As soon as the engine revs mount off tickover, it is just as sweet as it has ever been, but as it settles to tickover it sounds dreadful. Tickover has also risen by about 400 rpm but even when I knock that back it still sounds rough. On opening the bonnet the engine is not shaking any more than normal (though from inside it sounds like it is) and all the HT leads are in position and removing each in turn has the same effect for each cylinder.Performance doesn't seem to be affected and once revving it sounds normal and smooth.


You have some strange symptons there, an air leak could raise the the idle speed and make it uneven, a loose timing chain could rattle (sound rough) but should not effect the idle speed, a broken engine mounting could make a vibration (sound worse inside)....but should not effect the idle speed (unless it is pulling on the throttle cable due to engine dropped down)
I'm not quite sure weather there is a engine noise or you are just talking about a vibration as you say it sounds O.K. at higher rev's?
Does it have an unusual mechanical noise in the engine or do you think it is just an external noise due to rough idle?
Brian
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PostPost by: Dave_Newcastle » Fri Sep 22, 2006 8:19 pm

Roy

Your description sounds very similar to an experience I had - was a collapsed engine mount.

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PostPost by: theelanman » Fri Sep 22, 2006 11:15 pm

I was thinking engine mount as plays havoc with just about everything...espceially the carbs if your thakerys aint just so.....
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PostPost by: Roy Gillett » Sat Sep 23, 2006 11:45 am

Well done guys and thanks. Near side (exhaust side) engine mounting has collapsed.

I happen to have a new one and that side doesn't look too bad to get at.

I guess the increase in idle is due to the fact that the throtle cable choke cable and bonnet release cable are all held neatly together with a cable tie and as the engine has moved the throttle cable has a longer run and therefore has been tensioned.

What it reinforces for me is that you should ignore nothing. Every symptom has a cause!

Thanks again. Its out with the trolly jack and spanners now.


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