My 1996 850 20 valve starts and runs fine until it is fully up to normal running temperature. Then if I stop at traffic lights with the engine at idle, still under the normal load of the air-cond and auto gearbox it starts to misfire. The misfire is less if I put the gearbox into neutral and (heaven forbid) turn the air cond off. (You don’t want to do that for too long here, it is 34°C today).

So far, the plugs, plug leads and oxygen sensor have changed. The vacuum lines have been checked, even the 90° elbow behind the power steering pump and the small air leak from the top pipe of the Idle Air Control Valve fixed. The hot air pipe from the exhaust manifold to the air box was sealed long ago when the valve failed.

The dealer can’t get the OBD2 to connect to the system but there are no warning lights displayed.

Where do I go from here?

Cheers,

Andy