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Any problems with new oxygenated gas?
My 86 5000CS T occassionaly acts like it has vapor lock after restarting the car after it sits for
10-15 min after being fully warmed up. Feels like the injector lines have lost fuel pressure as the
engine misses until it is revved up a few times. It has done this every year after this oxygenated
fuel shows up at the gas stations. It is not as bad as it was last year before I replaced the injectors
after some were leaking. I have not checked my CIS system pressures lately to verify that the
several one-way check valves in the fuel system are working correctly.
Anyone else had this symptom?
Yes. I saw (see) this in my '83 UrQ. In my case (new injectors...damn near
new everything else too!), it was mostly a manifestation of the O2 sensor
taking a "while" to warm up and activate. This was made patently obvious
when I hooked up my duty-cycle meter to the FQ valve (there is a conve-
nient 2-pin "test connector" on my car, right by the coil; dunno 'bout
your beastie). After sitting for awhile (10-15 minutes to pushing an hour)
I can see the computer lock the FQ at 50% for 10-60 seconds or so, and the
engine was idling roughly and slow, although it "revved" just fine. Then
suddenly it will jump to 90%, and the idle smooths right out and speeds up,
FQ then dropping quickly to stabilize around 58-60% with a smooth idle.
The 60% means the base mixture is lean, so I adjusted the base mixture to
be a tad richer (holding around 45-49% FQ). Now the 10-15 minutes warm idle
is much smoother and happier until the O2 sensor heats up and kicks in.
This "adjustment" is maybe 1/8 turn of the mixture screw, so it is a fairly
sensitive adjustment --- and being just a tad off had exactly the obser-
ved symptoms . . .
I've come to the conclusion that a good "auto test meter" with 5-cyl tach
and duty-cycle ranges are damn near indispensible for an Audi owner. (Not
to mention this mailing list!)