What do you idle at?

[T33stat]

Hi all,

Some of you may know I have a mk2 project going on that I bought after being lead up for a few years, the MOT jobs have been done but it has what I believe to be a low idle.

It's still on its original carb, It starts on the button and the auto choke works fine (weirdly enough)

From cold it sits at around 1800/2000 and runs fine, as it warms it drops down to around 700/750 which is fine until you try to use anything, as soon as you draw electric from the battery it drops the rpm a little and the car shakes, stutters and eventually cuts out.

If you give it a little gas it's fine, but the second you come off and it drops down to the 700 area (just below the 3rd mark below the 1k range) it has issues, it's seems like the alternator isn't putting out enough to keep the car fed, I'm sure if I upped the idle to 1k with everything off it would solve it but just wondering what others opinions are.

Thanks :)

[bengould]

Should be about 850-900 if I remember correctly.

Ben.

[hiltow]

Warmed-up, mine is set at 950 rpm , though the figure quoted in the Haynes Pierburg book for a 2E2 carburettor is 750 +/- 50rpm, which seems too low (as evidenced by your situation).

There will be one component that's at fault (most likely) or one adjustment to be made that will solve the problem - the main issue with these carbs is that one particular symptom can be a product of various different components and setting, hence why most people don't have the patience to eliminate them one by one, especially when it comes to fitting a new part to it that makes no difference.

First, check that all of the vacuum hoses and connections are tight with no holes or splits. Also check the rubber carm flange mount for leaks. If the spark plugs have been in a while, check them to see of they're sooty as this will tell you whether the carb mixture is too rich (may be helpful later on).

From start-up on cold, it should hit almost 2000 rpm for a few seconds before cutting down to about 1300rpm until it lowers as it warms up. Several different components producing vacuum come into play during this process. As the temperature rises from starts from cold below 4 deg c the thermal timing valve (TTV - black round plastic thing on the l/h side) is open. As it rises further, or for starts above 15c the TTV closes, which enables vacuum to actuate the throttle plate actuator (big metal disc close by also on l/h side). This reduces the fast idle speed, which is aided by the waxstat and a series of springs and levers.

An electric switchover valve governs the vacuum at the throttle plate actuator - the voltage supply from the relay (black cube located close by that clicks when the ignition is turned on) switches on and off depending on whether the revs are above or below 1200rpm. If over, the voltage is cut and the TTV shuts. Vacuum at the throttle plate actuator increases and the pushrod on it is withdrawn. If below, voltage is applied and the TTV opens, vacuum at the actuator collapses and the pushrod extends to place the throttle plate in the hot idle position.

All the items in bold will need to be checked. Assuming the 'plugs are normal coloured, try adjusting the idle speed control valve slightly at the back of the throttle plate actuator, but make sure you know exactly what it was set at before to move it back to if it doesn't make any difference.

Other possible causes of a low warm idle speed are:

mixture too lean
worn throttle spindle
vacuum leak in carburettor base
blocked jet
mixture too lean (as you'll tell from the colour of the 'plugs)

Apart from the carb mount and mixture, wouldn't have thought these were the source of your problem.

[unknownmale]

I have an auto on a weber, idle is 1100 then around 900 under load, 850ish with the fan running if in traffic, but autos are meant to idle higher.

[T33stat]

I think the first thing is to increase the idle speed and see if it helps, I'm planning to build up a 1.8 lump with new gaskets and a Webber over the summer and drop it into the car, so looking for a short term fix :)

Thanks!

[mark1gls]

I have mine ticking over at 950 rpm as any lower and things in the start to shake and rattle inside the car.

[T33stat]

I notched it up a little and it's idling just shy of 1k with nothing else running, turn on all the bells and whistles and it drops down near 800... That'll do! :)

[teenspirit7]

Hi T33stat, did you notch up just the idle (at the back of the carb) or did you also change the fast idle?

Just wondering as I'm looking to up my warm idle speed?

I'm currently at 750 and I think it's a tad too low.

Cheers

[Nate]

My gt2 with a weber fitted currently ticks over at a shade over 200rpm. Keep meaning to adjust it slightly higher, but it seems happy enough so I haven't quite got round to it yet