My 97' 155 1.8 16v is behaveing odd lately, revs hunting at idle, going up to 2000 nearly every time i am stopping (pressing clutch). The counter drops quickly, falls a little bellow 1000, engine feels like it caughs a little (no lights come on), then it revs up to 2000, drops the revs again, then raises to about 1200, then it settles. Also my fuel consumtion jumped up drasticly (from 10-11 l/100km to 13-14 l/100km). Also if i drive it in second gear at around 2000 revs it starts to behave jumpy after a while. The local Alfa specialist diagnosed this is a air flow sensor fault, tried to change it with no effect, they also cleaned some flap in the air system and connected it to a tester which reported no errors. They said that one of the injectors is maybe dirty or i have a faulty lambda. They don't have time to investigate further before the new year. So i want to try few things myself.
I would like to know how to test the lambda and any other sensors which could cause this with a multimeter, which wires i need to connect. I searched the forum for this already but from the topics i could not work out the wires.