Re: Need help: 1986 spider engine running very badly

[Stacy Faught <onethumb@xxxxxxxxxxxxx>]

While I'm only a fair mechanic at best, a couple of things come to mind: A)  The variable timing device is not working properly.  On L-Jet Spiders, itis supposed to engage around 1700 rpm--below that speed the cam overlap isreduced for emissions reasons.  If the cam is not rotating to it's proper runningposition, then you would have a very rough running engine indeed.  There are onlytwo pins on the connector, so I'm assuming that you will see current eitherbelow or above 1700 rpm. B)  The throttle position sensor somehow shorted so that the 'idle' conditionis being sensed at all times.  It has three pins--bottom and middle pin shouldbe closed (zero resistance) at idle.  Once you move the throttle a few degrees, the switch will open and you will have infinite resistance.  At WOT, the top andmiddle pin will read zero resistance, but should read infinite the rest of the time.I'm not sure, but I'm guess that if the position sensor is sending an 'idle' signal to the ECU and you are at higher rpm, the ECU will think you have lifted throttleand are coasting in gear, which will cause it to lean out or cut the fuel.  Since youhave the throttle engaged, the airflow flap will be open, so you are sending conflictingsignals to the ECU.  Mabye one overrides the other---you'd have to find an L-Jet expertfor that answer. It could also be any number of other things....namely air leaks.  I doubt faultyignition would cause this to happen, but like I said before, I'm only a fair mechanic at best!   I would take the time to check all the electrical stuff first, since mostof the connectors are easy to reach and it only takes a few minutes. Hope this helps!Stacy'87 Spider Quadrifoglio  

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.


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).
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