Interesting carb fault please help

Hi there,
I'm driving a Golf Clipper 1989 1800cc 8v which has a Pierberg 2e carb.
When it heats up from cold, the revs idle faster and faster until eventually it idles at over 3000rpm.
If I leave the car stationary, once fully warmed up (10 mins?) the revs will suddenly drop to the normal 800rpm and everything will be fine again.
If I then go for a fairly fast drive (which takes plenty of cold air in the front of the car) after a while the revs will switch up again and it will again idle over 3000. I am obviously noticing this problem moreso now as the weather is getting colder.
If I then park up for a few minutes with it revving at 3000 it will eventually drop again.

What could be causing this?
A mechanic had a quick look today and told me it's not the Waxstat.
I had a brand new automatic choke unit bolted onto the side of the carb recently so I don't suppose it's that.

If I park up and switch off when the revs are high I get run on. The engine chugs for ages after I've walked away from the bloomin' thing!

Another guy had a similar problem HERE and I was wondering whether mine's the same.

Many thanks for any help.

Go over all the vac pipes like in that thread.  Pull each one off and inspect it - any dodgy looking ones replece.

I certainly will…but you'd think that if it were a hose the symptoms would be more "variable" rather than the "on" or "off" that I am getting. Like comparing analogue to digital.

I'll get me 'ose today then. Might buy it from Ronnie Corbett's shop……
"Got any 'ose"?

These 2E carbs cause nothing but bother, best idea is to get rid of it and replace with a Weber, you'll be better off performance wise, fuel economy and at least you won't need to fix it every five minutes !! I think they go under the guise of 'webcon' now.

cheers

Only thing is, the car is old and ?200 on something which is worth maybe 3 times that is hard to swallow LOL.

I have had my electrical meter out this lunchtime.
The thermotime valve thing on the back of the carb has a broken wire.
Only the brown one is connected and no the yellow/black one.
Should the yellow/black have 12V (IGN)?
I guess the brown one approaches 12V as the engine warms up (signal from a sensor)?

Is this how the thermotime valve works?

EDIT (AND GOOD NEWS FOR ME)……..
I pulled the two hoses from the thermotime valve and my car idled high. I then blocked the hoses with my thumbs and the car idled perfectly.
It must be the broken cable then.
Can anybody confirm that the yellow/black cable should be connected to 12V (IGN)?
I don't seem to be able to find the other end of the cable if you see what I mean.
All I have is a trailing wire from the connector which plugs into the unit

ayup mate, your carb will work fine without 'feed' (but needs an earth), the stat works from water sent (temperature) round the whole engine cooling unit, you can adjust how long it stays on by rotating the round aluminium cylinder on right of carb buy undoing (only slightly) them three positive nut thread screws and turning. i have never known a vacuum hose split but have known the advance diaphram perforate, its all bad get yourself a manual choke carb if you can, the thermotime thing dont rely on electrics it relies on luck :wink:

I had the same thing.. revved up to 3k and ran on like a deisel when u cut ignition. The plug that the two wires you mentioned had come off.. plugged it in and all was well. I can pop out to the car in a while and see if i can see where the one u need goes

Stu

87 Cab

I had exactly the same problem and spent ages trying to work out what it was. I just gave up in the end and got a webber conversion and its the best thing I did I really recomend it !!!!!!!
its a lot simpler !
just make sure ur heat risers are cleaned out when its done !

that valve is responsible for controlling the 3/4 point unit, if disconnected/broken the plunger will extend and hold the idle up.

Get them wires fixed and it should be fine again