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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!)