Rough idle

[andyhay]

Hi all

I picked up a new ( to me) plus 2 on the weekend and after a long drive home on the freeway the idle was very rough. Shaking the car rough. As soon as I take off it seems fine and has plenty of power. revs over about 2000 are smooth. It's on Webers and has been fully restored. Last time I drove it a few weeks back the idle was very smooth. It has seen very little use by the previous owner - so probably hasn't had a spirited drive in a while. Any diagnosis would be much appreciated. Thanks

Andy.

[rgh0]

Idle mixture, carb balance and ignition timing are all potential ocntributors

cheers
Rohan

[nigelrbfurness]

If it was OK before and not been touched since, try taking out the slow running jets and blowing them through also check there's no corrosion or debris in the carb bodies where you've removed the jets. I'd also try a new tankful of petrol if its been stood for a while.

Nigel F.

[William2]

If all else fails I would remove the carbs and strip them and blow through all the jets and body holes and channels with compressed air. It only takes a small amount of dirt to mess things up. I have just done this and it seemed to do the trick.

[andyhay]

Thanks guys

I will try blowing the jets first. I have been in touch with a very helpful guy from the lotus club who is meeting me on Saturday to have a look - he suggested blowing the jets as well. If that doesn't fix it I'll work through Rohan's suggestions. I'm pretty amazed at the eagerness to help within the lotus community - thanks so much.

Andy

[rgh0]

Richard is a great guy - even if he does like Europas! i have been teaching him how to build a good twincam as he has spent most of his time working on Renaults. He has a Lotus 47 in bits that he is restoring plus a series 2 Elan that he has almost finished restoring. A S2 Europa with nice big hot engine as his everyday car (cross flow 1800 engine to Gordini specs) Also a S1 Europa awaiting restoring and Alpine A110 also waiting. He knows more about Renault / Gordini / Alpine engines than anyone i have met.

cheers
Rohan

[andyhay]

Hi All

A quick update - I went to see Richard and he adjusted the balance between the carbs where the throttle cable connects. The idle is a lot smoother although still a little rougher than I expected. It may just be the way the twincam engines run?
I really enjoyed the trip to Richards man cave - so many loti in various states of assembly. Also had a sit in his Europa - so low, I can see the appeal.

Thanks all for your assistance.

Andy

[rgh0]

Lots of potential issues at the next level of detail once you have the carbs adjusted to get a stable idle. The twin cam will never idle like a modern fuel inject twin cam four but it can come close

Things like the following are areas to work on:

distributor thrust bearing wear and cam lobe wear
timing chain and sprocket wear and correct tension
idle mixture
plugs heat range
throttle plate position and balance between individual throttles in the each carb
details of the engine build in terms of combustion chamber size and compression variation between cylinders
details of the exhaust system you have fitted

years of fun in pursuit of perfection

cheers
Rohan

[reb53]

And make sure you don't have a float with a hole in it that has allowed the float to fill up with fuel.
Found that seems to mess a lot of things up......