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Why does it go "Pop!" - Induction/Turbo/Manifold/Exhaust - The Lotus Forums #ForTheOwners Jump to content


Why does it go "Pop!"


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Took the car out for a couple of short runs as a shakedown after some recent work.

Upon return, I do what I always have done - which is to leave it idling for about 3-5 mins just to let everything settle down before turning it off.

After I turn off the ignition, I can now count about 5 seconds, and there is a little "Pop" just like a small backfire.

This also happens even when the car has been running on the drive and getting up to temp.

Could someone explain why this happens ? - and if it is OK to leave as is, or is there another opportunity to fix something before it breaks ?

 

PS - Turning the stereo up doesn't fix the problem 😉 

 

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Our friend's '85 produces this shutoff POP as well. Especially after I drive it...

 

For that matter, so does our snowblower...

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Atwell Haines

'88 Esprit

Succasunna, NJ USA

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  • I had the same thing on a NA engine after I had wraped the exhaust in heat wrap, I had a high idle so after turning the engine off it still sucked in some air/fuel mixture, this then went into the hot exhaust manifold and 2 sec after turning it off BANG, (but only on a hot engine)  I lowered the (too) high idle back to 850 and this (for me) solved the problem.  
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As mentioned, its almost certainly unburned fuel igniting in he exhaust.  But to do that, something needs to be pretty hot.  I'd probably double check that your ignition timing is to spec and your mixture is not too lean.   Maybe also check that spark plugs are correct grades?

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5 hours ago, jonwat said:

It's a little explosion in the exhaust system so eventually it will blow a hole in a weak spot. 

So you are saying, Lotus planned it that way to advise owners of a dodgy exhaust?😆

 

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Atwell Haines

'88 Esprit

Succasunna, NJ USA

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