Motronic error states / limp home mode

[Orin Eman]

> it is a '93 Audi S4 motronic, and I believe I'm getting the Manifold pressure sensor
> failure mode ( due to it not agreeing with the air mass sensor, due to running
> 23 PSI of boost ) making it enter limp home after about 10 seconds on boost.

I'm not surprised.  It has a 2.5bar sensor and 23 psi is over 2.5bar.

> How long does the ECU take to recover from a power interruption (reset)
> thought two was that I would reset the ECU at 5 second intervals when the boost 
> exceeded 15 PSI ( say .02 sec pulse of the supply voltage ) ?

Too long.  At least one revolution to resync the crank/cam sensors.  Then it
will have forgotten any knock retard it had.  Get a spark at the wrong time
and you'll likely bend a rod at that boost.

> Thought 3 - which registers are responsible, I can cut a new EPROM if I have to,
> but I'd rather not if it isn't necessary.

> If someone has mapped one of these to 23PSI I wouldn't mind having the code ?

That would be EPROMs.  There are two CPUs in the ECU, one for fuel/timing
and one for boost control/knock retard.  You would need a 3bar pressure sensor
too which entails many more changes in the tables.

This has been done, but it costs significant $.  Talk to Ned Ritchie
at Intended Acceleration... www.intendedacceleration.com for information.

Orin.