1992 400E - rough Idle & hesitation

[tkplay]

My 1992 400e which I have owned since (1997) 79,000 miles and now has 243,000 miles is finally having some of the traditional problems associated with this model.

Car gets oil changed ever 3,000 miles, ATF 30,000 miles. Car is immaculate by my standards. I am a light DIY, Stuff like the hood insulation, brakes jobs, cooling fan housings, door locks, washer fluid assembly, shocks & struts, belt & tensioner replacement, etc.

I also did the plug wires about 40,000 mile back.

Car was running Ok when I decided to have my indy replace the cam chain & tensioner (loud at start up) for the first time (242,000 miles), Well of course when removing the valve covers the air hoses broke and the wiring harness cracked, all original. Now the car after spending about $3,300 has a new intermitting problem. Occasionally after car warms up hot it feels like the car drops a cylinder and idles very rough, then for no reason (sometimes an hour later) the car will runs good. Also there is a slight hesitation now when starting out from low idles. Above 1000 RPM the car is running fine all the time. Gas milage has dropped 1 - 1.5 miles, down to 19 miles per gallon.( This may be my transmission though. I am thinking it may be the air mass meter (original), but why now after all the other work has been done. Has my indy done something to cause the problem? Could my new wiring harness be defective with a broken internal wire with loose connection? We took the codes off the computer and had many since it hasn’t been cleared in years. I am waiting to check again tomorrow.

I have considered Fueling pressure, throdle positioning sensor, Broken plug wire, I have had transmission fairing problems and replaced the kick down cable. Could the Transmission in any way cause the idle to be rough?

I would appreciate any Ideas.

I love my car, I guess I am a fool to keep it so long!