[s-cars] code 2224 (Over boost condition)

[Jack Gagnon]

Hello,

I have a problem in my 92 S4.  The car has a hybrid KKK small 26/Air
Research T04 turbo that was on the car when I bought it about a year and
half ago. When driven hard, I get a sudden fuel or boost cut-out that sends
the car into a low boost mode until restarted.

I attributed my problems to the TAP chips that triggered an ECU code of 1111
(ECU malfunction or invalid checksum).

About 4 months ago I purchase a Lehmann stage III chipset to replace the TAP
and the code 1111 went away.  I then started to see another code 2222 (ECU
Pressure sensor defective) so I replaced the TAP 3.1? bar sensor with a
Bosch 3 bar and things are getting better.  The wastegate frequency valve is
finally working to control the boost.  Prior to replacing the ECU pressure
sensor boost was only available by manually adjusting the spring pressure to
the desired boost level (not good practice!).

Now it appears that the wastegate frequency valve is having trouble
controlling boost evidenced by code 2224 (Over boost condition).  I am not
sure what to do next.  The frequency valve is functioning properly most of
the time, but does exhibit some strange behavior.  Under tall gear long full
throttle applications, the boost gauge needle flutters (enough so I can hear
it).  There is no fluttering while rowing through the gears.  The fluttering
appears to be the frequency valve not being able to keep up with the turbo
resulting in high and low boost cycling.  Another symptom is a cut out at
about 6300 rpms in 3rd.  The cut out disrupts the acceleration abruptly and
sends the car into a low boost limp mode.  I have had this happen
immediately a few times when making a really hard shift from 2nd to 3rd.

Should I replace the frequency valve?
Can it be cleaned and lubed?
Is the turbo just to big for the stock controller?
Do I need an aftermarket controller?

Thanks

Jack

Overboosting and Limping in K-port, ME
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