[1988 90Q MT]Fault Codes

[Huw Powell]

> I cleaned out the idle air valve, poured a tiny amount of 5w30 inside, and
> managed to free the adjusting screw.  The valve inside moves very smoothly.
> Before I had read Huw's response ("paritally open at rest state"), I screwed
> the adjuster in 1 turn so that the valve was closed fully at rest.  It
> seemed to me that the valve had gone PAST closed and was slightly open
> again.   I thought I had read that the car SHOULD stall when disconnecting
> the connector from the valve, which it does now, and didn't before. I still
> have a highish idle, and it still does the dance between 1k and 1.4k idle
> speed.  Huw, should I turn it in another 1/2 turn or so to open it slightly?

Uh, I didn't know they even *had* an adjusting screw...

you can also check that it actually responds to voltage applied (I think
12v is higher than needed and could hurt it, try lower first) across the
appropriate pins.  One will open it, one close it, as I recall.  Don't
leave it energised for long since it normally cycles fairly fast.

> I'm kind of thinking that the injector seals are leaking (will test
> tomorrow), because I pulled the upper intake and checked everything else for
> leaks and cracked hoses.  If I understand CIS correctly, leaks on the engine
> side of the throttle plates cause the idle speed to increase (at least when
> operating in closed-loop), and air leaks on the filter side of the throttle
> valve cause the Differential Pressure Reg (brand new on my car) to be at
> something other than 0mA current, but do not affect idle speed.  Is this
> correct?

on the first part you sound right - and the DPR will be driven above the
"middle" in order to add some fuel, once the OXS sees the lean mixture
due to the leak.  Leaks before the throttle plate will result in a lean
mixture (unmetered air) that has to be corrected as well, but prolly not
a high/out of control idle.

So try to nail down any possible air leaks, make sure that ISV is
working, and see where that gets you.

What kind of shape are your intake manifold mounted ECU ground wires in?

-- 
Huw Powell

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

http://www.humanthoughts.org/