Car is a 91 940GL with B230FB, Bosch LH2.4 & EZ116K.

My 940 has been suffering a somewhat dangerous idle problem lately. Yesterday, I started the engine (cold) and the idle was a little slow ~600-700rpm. While reversing the engine suddenly revved up and I had to slam on the brakes to prevent backing into a fence. I wasn't touching the throttle at all - only the brake. It lasted only a second or so and then settled down to a normal idle and was fine for the rest of the trip of about 10 kilometres.
It has done this a few times over the past 2 weeks or so but yesterday was the worst example.

Also lately when the engine is started hot it will idle slowly ~500rpm or less. Sometimes the throttle needs to be opened a little to prevent it from stalling. Then it suddenly revs up to about 1300rpm for a second or two and then drops to a normal idle.

I've had this problem in the past and it has been solved by cleaning the throttle body and idle valve but this time it hasn't worked. They are both clean and the throttle switch is correctly adjusted.

I've no idea where to start looking. Any advice would be very much appreciated. Help prevent damage to my beautiful 940!!!

Thankyou
Brad
91 940GL