If it's the "stappenmotor" (variator) you will also hear a ticking sound
like when the tappets (hydrauclische klepstorters) do not get enough oil
pressure.
The "normal" sound of the tappets will normally only occur just after
starting the engine and willb be gone in a few seconds as soon as the oil
pressure has been built up.
When the variotor is the reason it will not go away with the oil pressure
build up.

Defective variators used to be a typical FIAT/Alfa problem which came up in
the period 1999/2000 and has been solved in new engines built from June
2000.
Problem was a sub-supplier delivering faulty (bad quality) variators.
In those days even many cars had the variator changed more than once as they
replaced a defective one by a similar one with the same bad quality.
Therefor guarantee!!!
But with a 4 year old car????

If you don't have this sound, it looks questionable to me.

I would go for 2 different options.
Option 1
Specially the hunting rev's at idle (= closed butterfly valve in the
airflow) point to dirt build up in the outer circumference of the butterfly
valve of the air inlet
Option 2
Check the lambda probe in the catalist converter
--
Ciao from Holland
AlfistaGJ (Gert-Jan)
Alfa red 156 SW 1.8 Madeno tuned (2000)
Golden Montreal 1428700 (1973/4)

"Guus Obelink" > schreef in bericht
...
> Since a few months the engine of my 156 SW 1.6 is running poor from 1750
to
> 2500 rpm. If you try to run it at an constant rpm, the engine is not
running
> smooth (NL: de motor houdt in) and at idle the rpm varies from 800 upto
> 1300.
> The dealer resetted the motor management computer, but without positive
> result. Now he suggest to replace the electromotor (NL: stappenmotor)
which
> controls the throttle. The dealer said the had a good result on an other
> 156, which had the same problem. This electromotor cost about 100 euro and
> mounting will cost another 50 euro.
> Can anybody give my advise: Is this the cure for the problem, or are there
> other options?
>
> Thanks in advance,
>
> Guus Obelink
> 156 1.6 TS SW 2000
>
>
>