Need help: 1986 spider engine running very badly

["Damien Gaboury" <dgaboury@xxxxxxx>]

Hi all lister



My Alfa spider 1986 is garaged since two weeks. My engine is running very
badly. The engine starts well, but it seems to run lean, at such point that
the engine vibrate strongly and hesitate at above 2000 rpm. The symptom
appeared while cruising at moderate speed (100 km/h or 60 mph). Suddenly, the
car started to vibrate and hesitate. The symptom appeared like that. I then
realised that the problem was engine-related. I came back home running the car
in 5th at 2000 rpm.  Fortunately, I was not too far from home. All the gauges:
collant temperature, oil pressure were OK.



My initial guest was that the problem was fuel-related (not enough fuel
pressure). So I replaced the fuel filter and the noisy fuel pump yesterday
without much success.



I thing that the problem is not related to a particular cylinder or injector,
because the engine runs fine (not perfect) at idle (about 900 rpm). Also all
four injectors work (I can hear the click - click sound of closure and
opening). All four spark plugs have the same aspect: typical light black
carbon coating. Furthermore, It really seem to be a mixture problem, as
suggested  by the fact that there is 0 voltage value at the oxygen sensor,
whereas two weeks ago, I have fine tuned the car at about 0.5 volts (measured
with oxygen sensor disconnect to the ECU).



Below are some parameters to help me to diagnostic the problem.



New item on the car:

Ignition: rotor, cap, ignition wires and spark plug (Lodge)



Fuel: fuel filter, fuel pump (both replaced yesterday), fuel rack hoses,
injector seals and some fuel feeding hoses.



Air:  air filter, 4 manifold hoses.



Engine Timing is perfect (just checked), valve clearance are perfects,
cylinder compression: 180-185 for all measured 3 weeks ago. I cleaned the
vapour phase separator this winter, and there is some oil in the tube going to
the oil sump. Head gasket OK: Oil is perfect, no coolant within it, no oil in
the coolant. I can hear the sound of the pre-pump running in the gas tank.



Here are my guests:



Ignition problem: 1) Bad coil (how to test it?) or 2) bad ignition ECU (any
tips for testing it ?)



Fuel related: 1) bad pressure regulator or 2) clogged fuel hose somewhere or
3) Bad ECU or 4) faulty sensors ?



Air intake: 1) bad flow meter: the flapper door works normally, but I don't
yet measure voltage and resistance at the pins. 2) Leaking air: all hose
tested OK.



Exhaust gas: Clogged catalytic converter. This is a typical problem on my Audi
90 Quattro. Could it be possible on the Spider ? How to test it ? The car ran
very rich until my recent tune-up.



Any other tips will be appreciated.



Please help me, my wife don't find the situation very funny. In fact, she
pointed out that I have spend more time working on the car than driving it
since I bough it last July. I am sure that all of you understand that delicate
situation.



Regards.


________________________________
Damien Gaboury, Gio., PhD
Scientifique de recherche, CONSOREM
Universiti du Quibec ` Chicoutimi,
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