Car: 91 940GL B230F Bosch LH2.4 & EZ116K.
When starting from cold, the engine behaves as though it is running on 3 cylinders. It has also stalled a few times from a cold start. Seems to run OK when warm but sometimes idles slowly ~500 rpm. This morning though it started up and idled fine but after about 3 mintues driving (engine was almost fully warmed up) I went to accelerate up a hill and the engine stumbled for a second which it has never done before.
A couple of weeks ago I found that one the little threaded contacts on the end of a spark plug had come unscrewed (don't know how) and so the lead was just sitting on top of the plug. I fixed that up and the engine seemed much better but it's started acting up again. Warm starts are OK although sometimes it will idle slowly and the Lambda Sond light comes on but goes off as soon as I press the accelerator.
Spark plugs are good, I havent' checked the distributor cap & rotor yet (do that tonight). There are no fault codes logged. What are the possibilities? I'm thinking:
Injectors
bad contact somewhere
Air mass metre (do these play up then come good again or do they fail for good?)

Any help appreciated.
Brad
91 940 GL