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Re: 88 MB Urq questions

   >> > As for the US MC engine, it forgets about the O2 sensor pretty much
   >> As you showed, the MAC12D is a cut-down MAC11.  I would not expect any
   >I just remembered something else that may be of interest.  The MAC11 uses
   >a base duty cycle of 50% for controlling the mixture via the O2 sensor.
   >The MAC14 (some 89 MC engines and later) has an RPM/MAP based table
   >of base duty cycles!  So, the fuel metering needs compensation to
   >try to maintain a given A/F ratio.

   I have been following this thread with interest, and I would like to put
   some questions up for grabs regarding my Ur-Q.
   The previous owner appears to have replaced the engine with a MC, and
   definitely installed a MAC11b on my 83 Ur-Q.
   My car has a problem similar to the one reported by Phil on John's car.  In
   my case it accelerates rapidly until it gets to about 4500-5000 RPM and then
   sits there surging taking forever to get to 6000 RPM.

Sounds like the stock (U.S. trim, anyways) cam, to me. Assuming you're
not getting fuel starvation . . . (check O2 voltages!)