Firstly this is only for some technical interest. It sure has me scratching my chin. It's not a major issue as a new engine will be going in quite soon.

Engine is B200K. So I drive somewhere across town, let's say to the supermarket. Engine is warm when I get there. I return to the car 30 mins later and go to drive away but the engine refuses to idle unless choke is used. Bear in mind engine is still warm and should idle fine. I use choke to bring the engine to a reasonable idle but it will be erratic, fluctuating about 100 revs in each direction.

So everyone's thinking carb gaskets right? But get this - you slow down for some lights. Engine stalls. Bump start will restart the engine but problems still persist. Long journey will not resolve the issue. However, stop the car, turn ignition off and let engine stop. Start car again and it runs perfectly! An electrical issue. Electrical issue on a carbed car.

The only thing I can think of is something to do with the renix. But I'm seriously stumped! It's more a chin scratcher than anything, I'll probably only try to fix it due to curiosity.

What you guys think? Witchcraft?

Fuel boiling/vapourising in the bowl, possibly due to stuck needle valve?

When you turn it off, it removed vacuum from the bowl, lets it come back to level and sort itself out?

Ah yes that would make sense as 1 or 2 times if I've given it a good dose of man foot it has also cleared up.

Sorry for hijacking this,
I got a similar issue in my 340, but mine is a 1.4 B14-4E.
Even warm, it refuses to idle without the choke on and sometimes, in lower revs, i hear some metallic clicks, very strange.
What can it be?
One of the carb gaskets is not in very good shape (The one between the carb and the lower part of the intake, which i don't know the name )
That black thing.

That's doesn't look like the right carb for a 1.4?

The picture is randomish, from a bmw e30.

Chris_C wrote:Fuel boiling/vapourising in the bowl, possibly due to stuck needle valve?

When you turn it off, it removed vacuum from the bowl, lets it come back to level and sort itself out?

What needle valve? Are you talking about a stromberg B19A? This is a B200K with solex downdraft very reliable.

Sounds like an air leak somewhere, again carbs and manifolds are reliable, but could be an odd internal fault.

Renix also is very reliable, loose flywheel sensor?

Other odd issues are blocked or leaky breathers and nipples, subsequent incorrectly adjusted mixture and tickover.

Fuel pressure, dodgy regulator thingy?

I was meaning the floats needle valve that allows the fuel into the bowl so the bowl level is at constant height.

The 34/34 is reliable, but it has the same plastic piece of shit floater as in the 28/34(b172) carb, i suspect it could be aoaking up fuel

To me looks like EGR valve typical problem when stuck from deposits.

Think i got a renix unit in my garage if you get desperate that you can try, got a carb aswell but that wont help you as its tuned to run on an injection engine long story to do with when i bought the car n the guy changed badly! Worse than my engine conversion lol

Ah no worries bud, I'm putting up with it until the Sigma is on the road.

I vote EGR jammed open(recirc).