high rpm + high boost = stumble

[Kneale Brownson]

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This may be totally off-the-wall anecdotal experience, but in my 200q20v,
for about the last six months prior to the fuel pump failing completely, I
was experiencing occasional stumble under WOT acceleration when I got into
the 5-6k rpm range.  This would be a third gear circumstance mainly, so I'd
be at 1.6-1.7 bar in a stock 20v.  With no other change than the new pump,
the engine spins up as happily as it ever did for me.


At 03:49 PM 01/18/2002 -0800, Bernard Littau wrote:

>My 5ktq is experiencing a stumble or mis-fire at high boost and high rpms.
>I would dearly love some advice as to how to best diagnose this problem, and
>ideas as to what the problem might be.
>
>High boost is 1.6 - 1.7 bar, I am running a 1.7 bar spring and no WGFV input
>to the WG.  ECU is good to 2.2 bar.
>
>At any rpm, under low load and low boost, the car seems fine.
>At low rpm and high boost, that is 5th at 3000 rpm, 1.7 bar, car seems to
>run fine.
>At high rpm, high boost, that is 3rd, 4000-6500 rpm, 1.6-1.7 bar, the car
>stumbles or mis-fires.  It's not a subtile stumble, either.
>
>The car is an '88 5ktq.  It has a new turbo, and the intercooler has been
>converted to single pass.  I have great confidence that there are no leaks
>in the air induction path from air cleaner to TB.  I do believe I have a
>small leak somewhere in the manifold (a hose) as my idle is now at 1000 or
>so.
>
>What the problem is likely not:
>I just replaced the wires, plugs and cap with new.  Plugs are: W7DTC 0.8mm
>Rotor and distributor are 3 months old.
>BOV has been removed and there are currently 2 pieces of 1" dowel in place
>of the BOV.
>
>I just replaced the turbo( IA RS2), timing belt and WP.  I also put in new
>injectors -- everything beyond the flare-nut fitting is new.
>
>The car ran fine at >1.7 bar at any rpm before I did the turbo and belt and
>injectors.
>
>Any thoughts are welcome and appreciated.
>
>Best,
>
>Bernard Littau
>Woodinville, WA
>'88 5ktq
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