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Stumbling when pulling in 1st gear - Fuel System/Carbs - The Lotus Forums Jump to content
Paul Coleman

Stumbling when pulling in 1st gear

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My car sometimes stumbles when I'm pulling away in 1st gear. The carbs were balanced a short time ago and the mixture set down at SJ Sportscars. It's difficult to explain the symptoms but it sort of coughs and splutters but then picks up. I haven't noticed it in the other gears. Anybody got any bright ideas?

Paul.

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Not that it's helpful but I have what I think is the same problem with my 90 n/a

I get an off idle stumble in first and also a similar coughing if I try and accelerate from cruise at low revs in a high gear.

If I let the car pick up slowly or rev it hard it's hardly noticeable but under 'normal' accelleration it's there.

Refurbishing the carbs and balancing them has improved it but it's still there ?

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I'll double check the timing and re-check the carb balance. I was wondering if it could be due to the accelerator pump rods needing adjustment. Both my carbs have been fully stripped and rebuilt.

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Or try giving it a few more revs? There's not much torque to get the car rolling and most folk who have tried to drive mine for the first time stall it though lack of revs.

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What! You let other people drive your car? Have you taken leave of your senses man? Hahaha

I haven't noticed it before only this weekend.

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Hi Paul,

I had a similar problem on my S1, I also had them set up by S&J. I increased the size of the idle jet as this is incorrectly named, its nothing to do with the idle but is the transition between no throttle and opening up the main jets.  The difference was remarkable.  You can get new jets from Dellortos in Reading who are very helpful.. They are not expensive and if it doesn't solve the problem you can change them back.  Hope this helps.

Alec

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I agree with the above comments.

My engine pulls from low to high revs in one continuous move now. It has been different when I bougt the car 5 years ago. It is all in finding the right ignition timing combined with carbs setup.

Things that improved the engine reaction in the past were.:

1. carbs ; setting and controlling the right fuel level with the floats.

2.carbs : increasing the idle jets from 55 to 58 ( my engine is a 2.2NA)

3.carbs : reballancing them about every 3 months.

4.adjusting the ignition timing at idle from before 8°BTDC to now 12°BTDC (this gives about 32°BTDC at 3500rpm)

 

Geert

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