My 940 (945 wagon) is a UK spec car with a B200F engine - 2 litres, non turbo.

I've got a minor issue with the idle speed. Normally starts and idles at around 750 rpm, very stable. After a run along a motorway at 70 mph or so, the idle settles back to around 1100 rpm. However if I switch off and switch back on again immediately, the idle is back down where it should be at around 750 rpm. So it seems that a high speed run is making some change to the engine which can be immediately cancelled by a re-start?

I have cleaned the throttle body and the idle air control valve, and checked that there are no air leaks in the induction system.

Any ideas please? Not sure whether it is inconsequential or an indication of something which I should be dealing with?

Many thanks

OwenF
Scotland

Hi Owen,

You've described the exact behavior of our LH2.4 cars when they lack a signal from the speed sensor which drives the speedometer and ABS (if equipped) electronics. The on board diagnostics verifies this by posting a DTC (diagnostic trouble code) of 311.

This VSS (vehicle speed signal) needs to come from the speedometer to the fuel computer, so if your speedometer is working OK, the problem will be in the circuit wiring, most likely at the back of the instrument cluster.
--
Art Benstein near Baltimore

Behind every great man is a woman rolling her eyes.