M104 hesitation - 300SL

[bhatt]

Hello all,

I am having a hesitation problem with my 1990 300SL (CIS fuel injection). Here are the details.. what should I look at next???

Problem:
-Hesitation when accelerating from idle.
-No problems with starting engine, idling, or once car has started moving. Accelerating from 5mph-60mph is perfectly fine!
-Anything other than light pedal pressure causes it to bog down for a second before it accelerates. Hard acceleration causes it to stall!

Conditions:
-Happens consistently all the time (cold weather, just after starting, when fully warmed up, etc, etc.)

What I've done:
-Replaced fuel filter
-Had fuel injectors flushed/cleaned
-Replaced air filter
-Replaced cap, rotor, spark plugs (but not wires - they are in excellent condition)
-Sprayed spark plug wires on both ends with mist of water while running
-Looked at wires in dark (no arcing seen)
-Pulled one spark plug wire and tested - 1230 ohms (spec says max 1200 but I'm sure that's not the problem since it's so close)
-Visually checked for disconnected vacuum hoses (none found)
-Cleaned throttle plate with carb cleaner
-Cleaned air temperature sensor with electronic parts cleaner
-Ran car at 2000rpm and pressed on throttle microswitch (the deceleration fuel cutoff switch). Car slowly dropped a few hundred RPM in and went back up when I released the switch.

WHAT'S LEFT? It's driving me crazy! Not sure where to go from here?!?!?!

Any help would be appreciated! This is such a simple fuel injection system but it's driving me nuts.. car is virtually undriveable...

Thanks
Neal