Hi , I have the following problem

Cold start idle speed is initially about 500RPM (car nearly stalls).
It then increases gradually to about 1300RPM after 5 minutes.
It then stays too high for about the next 20 minutes when it will gradually slow down to about 600RPM.

The car used to run very rich for about 2-3 minutes after a cold start so I adjusted the arm in the Warm-Up Regulator to stop this.

The car has no O2 sensor (it is Australian).

I have the factory manuals and wonder if the problems I have above are due to the Warm-Up regulator ? I have checked the auxilary air valve and it seems to open and close correctly.

The Bosch authorised dealers in Sydney tell me that you cannot adjust the Warm-Up regulator (but I know that you can).

Any idea what I should do ?


thanks
Doug McCutchan
W126 1983 280SE

The best thing to do in this case is to connect the fuel pressure gauges to the system and allow it to cool and then crank it up.

If you can't get to the gauges then replace the warm up regulator after you have checked the accumulator.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

The warm-up fuel mixture is dependant on having the correct fuel pressure at the correct engine temp. This is the job of the warm-up regulator! Sounds like the reg. is out of adjustment. To correct the problem the fuel press will have to be readjusted. At 20degC the pressure should be 1.4-1.6bar, & when fully warmed-up the pressure must be 3.4-3.8bar-both pressures w/engine running. The system pressure should be 5.4-5.8bar.