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Although I do not own a GTA, I am posting here, since manny more GTA owners did CF2 conversion than 166 owners, and therefore I believe you are more experienced in that area and can offer better help.


Anyway, I have a 166 with 3.2 V6, which I got converted to CF2 exhaust manifolds. And here is the strange issue.
At MOT testing, when car was still with CF3 setup, all went fine. But this year, with CF2 setup they could not read rpm properly - readings were constantly jumping from lets says 650 to 1200, and back to 900, and so on - when the car was at idle with constant 750 rpm.
Another issue was with lambda voltage reading, which was a little bit over the upper limit.
Someone tried to convince me that this is because of CF2 conversion, which I do not believe to be tha case, as it makes no sense to me whatsoever.
Emission test went through fine, by the way.


As I was thinking about it, I came up with another possible reason for this. New alternator was installed sometime before CF2 conversion, but it works fine, with 14.27 charging at idle, so I do not think it could be the issue.

But I had a water leak, where water was pouring on a connector, that, according to official Alfa dealer, contains GROUND for the alternator as well. Because of that leak and corrosion inside the connector I had some issues like: defroster grid not turning on, random dashboard lights coming on if it was raining heavily, once I got the alternator red dashboard light as well for a second,... and after this connector was cleaned of corrosion and water leak sealed, those issues seems to go away.
So it could be that after this the alternator GROUND does not have a proper contact, which is now causing problems with MOT rpm reading?

Another thing started to happen after water leak and connector were fixed: for the first time I got cat/lambda error - could it be from to high lambda voltage, and therefore rich air/fuel mixture? I also think the consumption got a little bit higher.
Before that, I was driving the car for few thousand miles without any lambda errors with CF2 exhaust manifolds.

Btw - primary lamdas are new, cat is new, I am also using lambda fakers on secondary lambdas to avoid errors... and the engine runs smooth and fine.


So the question - is it CF2 conversion that is causing rpm reading issues at MOT or alternator/wiring issue, or something else?



Thanks for reading and replying this long post.
 

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Can't see how removing two Cats would cause the RPM reading to change.....!
Depends how they are reading the RPM, if it is off of the alternator then yes it could be due to your alternator swap.
 
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