high rpm + high boost = stumble

[Larry C Leung]

Man, you got me. Good luck. FWIW, I had 1 yr old 8mm Beru's in my car
recently, tossed them for Bosch, and it no longer stumbles. Have you
considered the coil?

LL - NY

On Fri, 18 Jan 2002 15:49:09 -0800 "Bernard Littau"
<bernardl at acumenassociates.com> writes:
>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
>
>
>