Lotus Elan

not a sticking throttle

PostPost by: Gasman » Sun Nov 20, 2005 7:17 pm

Dear all,

I have a problem that seems like my throttle cable is sticking and the engine runs on with high revs when I back off the throttle. It seems to take ages to settlle back to the idle. I have noticed this most when in queing traffice when the engine was getting hotter.

However the throttle cable spings back with no hint of sticking and the linkage also seems free moving.

I would appreciate any advice before I leap in and take the Dellorto carbs to bits!

Regards

Mark
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PostPost by: JJDraper » Sun Nov 20, 2005 11:08 pm

Funny, mine does the same on Webers after a fast run. Last weekend, blatting down the M40, the idle speed went up for a while. It usually only happens after a fast run 10 miles or so at 80+.

I'm afraid I just get used to it, it soon settles back to normal. Could be fuel height - leakage past the needle valve. Opinions?!

Jeremy
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PostPost by: type26owner » Mon Nov 21, 2005 1:29 am

Guys,
Maybe I can help. When this happens are the carb bodies warm or cool to the touch? They should be at the ambient temperature or slightly cooler if the mean air/fuel mixture is okay. If it's cool reduce the idling speed by about 200 rpms and see if that helps stop the racing. You might be sucking fuel from the first progressive hole because the throttles are opened just a smidgen too much. If the carbies are hot then report that back here because it requires some rejetting. What is your miles per gallon rate of fuel consumption?

What temperature thermostat do you have installed?
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PostPost by: iain.hamlton » Mon Nov 21, 2005 12:10 pm

Mark, I have the same issue, but it is much better than it was. I suggest you check the following before diving into the carbs themselves:

1/ There is not the slightest vacuum leak on the feed to either the headlight resevoir or the brake servo. Disconnect the pipes and temporarily block the holes on the inlet tract and verify no difference.

2/ the balance is right not only at 1500 rpm as it says on the carbalancer instructions, but at tickover. What happened to me was that with the "right balance" at 1500 rpm, the front carb was actually more closed. At tickover, it was proping the rear carb open a shade through the balance linkage. Check balance at tickover by pulling off each plug lead in turn, one at a time; the engine speed should drop the same for each cylinder.

3/ For stiction in the linkage, not just the cable. Lubricate. I put an extra return spring and that helps too.

It still runs at higher revs when hot. 850 rpm warm; 1150 after a thrash. I can live with that. Perhaps we have all become used to idle control on fuel injected engine that works consistently.

best of luck,
Iain
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PostPost by: Gasman » Mon Nov 21, 2005 9:05 pm

Thanks guys; wills set to it and see what happens

Cheers

mark
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PostPost by: twincamman » Tue Nov 22, 2005 1:02 am

the idle should go to 600 rpm right smartly after you released the pedal -----don't drive with a stuck throttle ---[-hard to explain in court ] :shock: -ed -- dont close your eyes --you will miss the crash --
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