[W126 Coupe] Help trouble shooting 87 560SEC hesitation at take off problem.

[alal30319 at gmail.com]

All

I've been trying to trouble shoot my 1987 560SEC as it's having an odd
hesitation issue between 600 rpm and 1200 rpm. It's pretty severe and makes
crossing intersections hairy as the engine can choke out for a few seconds
before it spins the wheels and hauls away. I've been trying to counter by
keeping my left foot on the brake while revving the car so that I can avoid
the hesitation.

Here is what I have done so far in an effort to trouble shoot the system.

   1. Checked timing. Set to 27 degrees advance at idle (10xx rpm).
   2. Checked sanity and make sure that I was on cylinder number 1 and that
   my timing light was working correctly.
   3. Replaced black electronic device on the side of the fuel distributor
   with another one - no effect.
   4. Pulled valve covers to check cam timing mark and both appeared within
   spec (chain will need to be replaced soon however as guide rails are black).
   5. Checked throttle plate on air flow meter was in the right position and
   not too high, thus causing the flow of air to block when pressing on the gas
   - everything seems OK here.
   6. Checked to see if the transmission was recently removed as this may
   mean the flywheel was incorrectly mounted - Transmission does not appear to
   be disturbed.
   7. Switched ICU with a known good one - still have the same symptoms.
   8. Replaced Bosch twin platinum plugs with NGK BP7ES - Did not cure the
   problem.
   9. Adjusted mixture - No effect.

The car still has the green wire to the ignition unit which I understand
must be old as new ones are black and can cause running issues so i'm going
to try to replace that next.

Any other thoughts or insight would be gratefully appreciated.

With best regards

Al
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