Wont rev above 1500 RPM then coold

[Leif Karlsson]

Huw Powell wrote:
>
> > Bought a not so new car a while a go: Audi Coupe, 90 2.3E (KE III
> > Jetronic). It has been messed with, probably allot... It's giving me a
> > headage.
> >
> > It wont get above ~1500 RPM then cold (about 15C outside right now),
> > sounds like it cuts of the fuel then it gets close.
>
> That sounds to me like an idle switch staying closed.  One thing the ECU
> does when the idle switch is closed (ie, foot off pedal) is kill the
> fuel for a moment if the engine is above about 1400 rpm.  This saves
> fuel when you take your foot off the gas.
>
> The idle switch is under the throttle body, and is part of a little
> assembly that includes the wide open throttle (WOT) switch, which is
> mounted on top.  Their wires come together and meet in one three pin
> connector.
>
> Start by unplugging that connector and measuring the idle switch
> resistance in open and closed positions...
>
> > I have adjusted the current to the pressure acurator (was way of, ~18 -
> > 22 mA, warm engine), it's now -2 to 5 or there about, that fixed allot
> > of bad behavior, but not the problem above.
>
> It is supposed to *fluctuate* around 10 mA, not sit steady.  If it is
> steady when warm, your OXS may be bad, or something isn't hooked up right.

It fluctuates grate. I do get some negative readings however, that's ok?
It should bee around 0 mA and not 10 mA for my engine, right? KE3 I
think, inlet manifold in two pieces, doesn't look like yours.

>
>  > I checked the temp. sensor
> > on top of the radiator hose flange. It works, (but I don't know if it
> > works _right_: about 1.78 ohm at ~70C and 0.48 at 90C).
>
> Remove it and test it in ice water and boiling water to check if its
> range is close to right.  I forget the specs right now, they are in the
> Bentley shop manual though.  It does sound a bit low form what I recall,
> though - I think it is supposed to be around 1500-2000 ohms when cold
> and drop to 150-200 ohms at operating temp.
>
> They are pretty cheap, and I would tend to go with the recommendation of
> soe that you simply replace it with a new one on general principles.

That should have been Kohm's, but still...

If it's nothing wrong with the idle switch I will just replace it and
see what happens.

>
> Have fun, and good luck!

The same to you Huw. Life is there to be enjoyed!

Leif