Re: O2 sensor & 75 TS

[Dougal Mair <D.I.Mair@xxxxxxxxxxxx>]

Hiya Oleg,

You wrote:
>This is a very stupid question, and surely a FAQ, but I can't find the
>damned thing (O2 sensor) in my non-cat '88 Alfa Romeo 75 2.0 TwinSpark...
>
>The general sense is confused:
>
>1. No catalytical converter -> no place to screw in the O2 sensor
>2. Engine management is Motronic ML 4.1 -> operates Ok without O2 sensor ?
>3. Can't see any hanging wires...
>
>I wanted to check the voltage, but no place to connect :) Just
>sometimes/some rpm ranges
>the car is somewhat "sluggish"... Could be the engine temp. sensor too?
>(at the back of the engine block)

My 75TS doesn't have an O2 sensor either. However, the manual I got from
Charters in UK doesn't show an O2 sensor. I think the O2 sensor was not
used on the 2L Twinspark engine only on the V6 ones. I may be wrong.

However, I also have the sluggish performance problem at differing times.
Sometimes when I accelerate I get a good kick in the pants from the old
girl, but other times she's really dead. What I have tried so far is:

Dismantled the airflow sensor and cleaned the potentiometer and check its
resistance. Also, checked the air temp sensor in the meter as well. I am
still wondering whether the airflow sensor is faulty as when measuring the
resistence and moving the airflow flap, the resistence increased until the
flap was half way open and then the resistance started decreasing again. It
doesn't seem normal to me. After cleaning the potentiometer the resistance
increased and decreased more smoothly. Perhaps some other digested would be
kind enough to measure the airflow sensors resistance and advise how their
resistance changes?

I have check the throttle switch and it seems fine.

I tried running the car on one coil and set of spark plugs at a time and
the performance was pretty much the same with no missing, so they seem ok.

I tried putting voltage on the valve timing advance solenoid and also
measured the voltage supplied to it at various revs and it all appears to
be working fine.

My next step is to try fuel type problems. I put fuel injector cleaner in
the fuel for a couple of tank fills and I got a marginal improvement.

I hadn't thought of the engine temperature sensor. I'll give that a go too.

Cheers,
Dougal Mair
Palmerston North
New Zealand
'89 75TS (Red)
'84 33 CloverLeaf.

------------------------------