M119 Owners with Rough Idle/Missing/Hesitation problems

[aldedmon]

Thought we could start a concise thread for M119 owners with Rough Idle/Missing/Hesitation problems.

My 92 400E had these problems and I changed out, as I'm sure most of you have:
Plugs, Caps, Rotors, Wires(X2) - was still missing
New TBA and rubber sleeve and cleaned MAF - was still missing, but no longer hiccuping/cutting out
All vacuum lines/connectors - was still missing
Disassembled and reassemble the intake(there are rubber grommets that hold the upper and lower halver of the intake together, sort of like the "chinese finger cuffs")- was still missing
finally had the FI's purged under pressure using a purging solution and apparatus. Hesitation/Idle finally went away.

If yours is exhibiting any of these conditions start at the obvious/ easiest and work your way through these steps. At 180Kmi, all my rubber vacuum parts were brittle and needed replacement and the FI's need cleaning out.

Tom Woolner offered that the cause/cure of his problem " It was a broken piece of plastic(rubber sleeve) between the Mass Air Sensor and the
throttle
body. It was causing a vacuum leak, which caused rough idle. I
replaced the
caps, rotors, and spark plug wires before we found the real problem."

It seems to me that the rough idle that plagues these cars is more often than not related to a vacuum leak as opposed to an electrical(spark) issue. I've found that by starting the cars, removing the air box and spraying aerosol brake cleaner on all the vacuum lines,hoses and couplings that if these is a leak, this will detect them. The cars idle will surge or shut off. Hope this helps a member who is pulling his hair out cause he can't figure out what / where the problem is and is cringing at the possibility of taking the car to the shop and spending a lot of $$ to have the problem MIS-diagnosed!