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S4 high speed miss
Calling all q heads!
I am having a problem with a high speed, high load, high boost miss / buck
that my S4 experiences on occasion.
It is a '93 S4 with 65,000 miles and a Hoppen Stage III RS2 kit. It is very
strong and runs very well for the most part, and it is a ton of fun. The
one problem I do have, however, is a miss under heavy load w/ high boost. I
get 30 psig max boost in the higher gears and on a continuous incline with
wide open throttle I can get a rather abrupt miss / stumble, it almost feels
as if an IC hose has blown. I am off the gas immediately so I don't know if
it would continue missing. Back on the gas and the boost builds back up
Driving solo with less than a quarter tank of gas and the miss does not seem
to come into play. Several people in the car, full tank of gas, uphill, 5th
gear, WOT, 25+ psig of boost and the miss comes back.
Major service 5,000 miles ago including the proper F5DPOR plugs. I have
checked the rubber boots on the ignition coils and they seem good. I have
yet to hook up a fuel mixture gauge to see if I get a lean condition upon
miss / buck. The computer seems to back off boost the way my TAP computer
did (albeit with a max of 30 psig as opposed to 22 psig). Two of us are
running the same setup (a S6 too) and we both have the problem since
stepping up to the Stage III setup.
I know the 3B motors running elevated boost levels have had problems and
that the conjecture has to do with the ignition rotors. How about the AAN
motor with its distributor-less ignition? Potentially a weak coil on my AAN
motor? Is there a way to check the coils?
Any suggestions would be greatly appreciated. Is 30 psig (3.04 BAR) just too
much boost under load? I tried running some octane boost to see if it made a
difference, but it did not. One would think that if the miss is detonation
related to the high boost levels that running higher octane would either
lessen the severity of the miss / buck ar at least its frequency?
PS I am off the list so please respond directly.