..have poured through several blogs and reviewed threads here....please forgive the trespass if I'm repeating previous queries. recent parent of an 89 240 GL which sat for several months according to longtime prior owner. tuneup & diagnostic work has gone from charmingly distracting to fairly frustrating at this point. all standard tuneup stuff done (plugs, wires, rotor/cap, fuel, oil & air filters). TB, AMM, IACV all removed & cleaned & TPS replaced with new when found not to work properly. all vacuum lines, oil pot & flame trap replaced. Fuel pumps, pressure & line flow all within specs. fuel rail & injectors removed..one not spraying evenly so put rebuild kits in all 4 after flow test & rechecked.
..discovered IACV not working when connected to Jetronic but operated fine when temporarily jumped at battery...intermittent internal ground from Jetronic to IACV but all other circuits good. OBD check revealed 312 fault code (knock sensor) but code cleared after sensor replaced. Installed spare Jetronic.....no fault codes & IACV now functions properly but idling issue after coming off initial high start idle remains.
..checked timing....according to Bentley, should be 12 degrees off top back but currently sets itself at 10 degrees of top forward..a full 22 degrees from where it should be?? I can turn the distributor & idle improves but then 'corrects' itself back to the 10 degrees forward mark... would be very appreciative of any feedback/suggestions at this point.
comfortable with pretty much ruling out a fuel problem...all circuits at all components have been checked & within specs..ground & voltage all good..Jetronic Fuel & Ignition brains circuits all check out. no mechanical evidence of an elusive vacuum problem and no current fault codes....haven't pulled timing cover...wondering if a tensioner issue or some other problem might be causing persistent timing advance???....thanks!