Idle lean out
Turbo Mini Forums

I've got this wierd problem that only started this week

The car drives fine, afr is good through the range, in and out of boost, but when I let off the go pedal and coast in or out of gear and then of course while sat stationary at lights etc the afr goes off the scale lean and the engine gives a little rattle to concur that the gauge isnt lying.

As soon as I pull away all is well again driving like a dream.

Where it get strange is this only happens once you start driving it. If I go out now and start the car it will idle quite happily, afr all good and last night I left it for almost 15minutes idling without a problem. Its only once you start driving and then return to an idle state that the problems start.

Any thoughts?

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

do you have a servo? could be a vacuum leak

mine does this, i have found from my data logs a cold engine ( mine) idles on needle station 1-1.2 but when it warms up the idle is on station 0-0.1 this is with 20/50 oil in the dashpot and a 12lb spring only way to get around this is set stations 0+1 the same or give it as touch more fuel at idle

Yes i moved to the darkside

Instagram @jdm_brett

hang on i could be talking aload of bollox, is the part throttle lean of plumbed in? a warm engine pulls more vacuum than a cold one ( again from my logs)

Yes i moved to the darkside

Instagram @jdm_brett

If you have the bi metallic lean out needle holder in the Carb from original OEM, This will be your problem.

I do have a survo but couldnt find any leaks or issued around there.

Part throttle lean off is blocked off.

As for the bi metallic lean out needle holder....pass! I rebuilt the carb 2000miles ago with a genuine rebuild kit but I couldnt tell you what the needle holder is. If this is the problem why would it have only just started happening?

Looks like it could be getting worse as it actually struggled to idle today without any driving involved. As soon as you apply any throttle it runs fine again, just idle thats the problem.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

the needle holders are all bimetalic, usually they shouldnt give a problem, but if theres no heat sheild under the carb it could be the case, However I'd look for leaks to start with, servo is a good shout, try disconnecting that and plugging the manifold to start.

there was (still is?) a thread onn here about converting the jet holder to non bimetalic.

When mine does this I tighten up the manifold nuts and the problem goes away.In other words a small air leak at the manifold face,caused by the nuts relaxing(!)

'Where does the engine go?'

thanks guys, i'll get on it this evening and see what i can find.

Edited by Simon on 30th Jul, 2012.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151