4kcsq cold run problem

[Huw Powell]

> My 87 4kcsq has an irritating cold run problem that I am trying to diagnose.
> I am looking for basic information on the sensors used to control the
> injection system and the control algorithm used.  Is there a site similar to
> SJM's that addresses the 4k NA engines?  Or is there a close similarity
> between 5k NA injection control and 4k I5 control such that I can use my 5k
> Bentley to troubleshoot my recently acquired 4k?  I prefer to understand the
> system before going into a random parts replacement frenzy.

If your 5k manual goes back to the 2.2 (1986?  1985 for sure), it's an
identical system.

> The problem occurs shortly after a cold start.  It starts well and idles
> well.  If I drive off immediately all seems fine for about 2 city blocks.
> At that point something begins to happen that will not allow the engine to
> exceed 2000 RPM either loaded or unloaded.  It appears like the fuel is cut
> off at 2000 RPM and switches back on when the RPM drops a few hundred below
> 2000.

Shooting form the hip, but btdt, and also the only thing on the system
that can really do this - sounds like your idle switch (under the
throttle body, shares connector with WOT sw.) is not "opening" as it
should.  it might be finally opening when you get the rpms up higher -
there may be a mechanical issue down there, too, making it so a wider
throttle opening finally lets the switch do its thing.

Anyway, it's easy to troubleshoot.  Unplug the two switches when the
problem is occurring and see if it goes away.

--
Huw Powell

http://www.humanspeakers.com/audi/

http://www.humanthoughts.org/