For the past couple of years my car has had warm up problems. The car will always start first time and will run okay for the first few minutes, but after about three minutes of running, the idle speed drops very low and the car stalls. I only experience this problem in the Winter though when temperatures get down to about 3 degrees C.

The car has a Pierburg 2B5 carburettor (with semi-automatic choke) and fast-idles at about 1300rpm initially. As it warms up, the idle speed gradually drops (as it is supposed to) until it becomes so low that the car stalls. The car runs fine once the engine reaches its normal operating temperature.

I have replaced the bi-metallic spring housing at the back of the carburettor but it made no difference at all.

The Haynes manual says that the fast-idle speed should be set for 3000rpm but I don't know whether it's absolutely necessary. I don't want to wear the engine.

I should be very grateful for your thoughts.

Kind Regards
Will

1986 Volvo 740 GL (B230K engine) 235k miles