A/F ratios under varying conditions update

Brady Moffatt bradym at sympatico.ca
Fri May 23 16:50:16 EDT 2003

Hi All,

83 urq stumble over 4k in 4th and in 5th under boost was the problem. I was
thinking fuel delivery issues, so I tried richening it up by the
idle/mixture screw. I know this is now way out of whack re: duty cycle, etc.
but what the hay, I'm just diagnosing, right?

Well, according to the AF meter, the O2 voltage at idle is 0.88 or so, which
is way rich. But now under full throttle in 4th I can get all the way past
5k and the O2 still reads 0.7 or higher and there's no stumble in sight.
Good power too. 5th gear is the same, though I didn't get much over 4k due
to speeding issues.

So, it looks like it really was a fuel problem.

Now what do I do? Add a shim to raise system pressure, then unwind the
mixture screw? I'll have the current fuel pressure number in a couple of

Brady Moffatt
Montreal, Quebec, Canada
83 UrQuattro with 52,000 miles
86 4ksq with 310,000km
86 4ksq parts car
72 Datsun 240Z with 180,000 miles
92 VW Golf with 200,000km FOR SALE
in middle stages of quattrosis accumulatus

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