I think you should run some basic checks on your warm-up enrichment by measuring the current at the EHA. There is special harness that you can use to do this, although you may be able to rig something up.

Here is what the CD says you should be seeing for a KAT engine as of 09-1987:

KOEO: 20 mA

20 seconds after start: 4 - 8 mA

60 seconds after start: 0 to -4 mA. At +20 degrees, the coolant sensor's resistance should be 2.3 - 2.8 kOhms

Temp at +80, fluctuating currrent reading, 230 - 290 Ohms resistance from sensor

My guess at this point is that your coolant temp sensor may be bad and is telling the brain not to enrich.

Good luck. Many posts on measuring EHA current.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe