Hey guys, my name is michael and i have recently bought a bmw 325e 1986 model, Ever since ive had the car it has had a very odd idle, it would jump slightly and drop down to its normal rev. I had a mechanic do a major service, changing muffler and rubbers in the steering column or something like that, the car was up on a hoist for well over 5 weeks. I have recently got the car back. Today i gave it a wash, my dad decided to take it out for a spin. When he got back the cars idle was sitting back at 2,000rpm and well over, it would drop to 1,500 and then jump back up to 2,000rpm then after a while it would drop to 1,000 rpm and drop to 1,500rpm and then back to the 2,000. I have no clue what is wrong with it. The mechanic claimed my engine was good. But with a little backyard try and fix it jobs, Me and my father discovered a loose plug that wasnt in its jack. This plug is on the left side on the engine bay, attached to another plug in the air intake. It is very short and must belong to somewhere near the left side of the engine or near the intake or radiator. I somehow think that this plug was loosely fitted when i bought the car, and on the drive it must of poped off. I think This plug has to do with the cars ecu computer control. Maybe the ecu doesnt find the car and is lost, this is maybe why its just lost in the revs, ur help would be apprichiated, i will how ever take it to the mechanic tomorrow but it would help with my pocket cause im currently 16 and have a low paid job. I've spend over 1,000 australian dollars on serivce and insurance so i dont have much money to thrown around, thanks guys
michael