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Discussion Starter #1
Hi
I have an alfa 147 2.0 ts yom 2005.sometimes I use the car and it works perfectly, then I go to start it again and it starts acting strange.when i turn on the ignition the car start to rev by it self then it turns off.when I try to press the gas pedal the car has no power and it is hesitant.then I leave the car for 30 mins and it starts immediately.I plugged multiecu scan to see the errors.it gave me air flow mass sensor, but I find it strange the problem is related.Any help?

Thanks
Riccardo
 

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To me it sounds like a faulty crankshaft sensor also called RPM sensor.

When a crankshaft sensor is faulty there is usealy no problem to start when the engine is cold, but if you try to start when the engine is warm it won't start and after a bit of cooling down the engine will start

But as you get a MAF error, have you tried to unplug the MAF when you have the problem to see if it make a difference?
 

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Certainly sounds like it could be the crank sensor.

When mine went on my GTV TS it cut out at a set of traffic lights. I had to spray some carb cleaner into the intake to get it to fire up so I could try and nurse it back home. However it eventually cut out again when I got stuck at another set of lights and I needed to get it towed to my indie. Sure enough he said it was the crank sensor which is notoriously hard to diagnose since it usually doesn't give an issue on cold starts, only when warm.

But before you do anything, get the engine up to temp and then shut it off and try and do a warm start. If it doesn't start, disconnect the MAF and try again. This way you can help to diagnose the MAF.

But I am leaning towards the crank sensor.
 

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Discussion Starter #4
HI
thanks for the quick replies.the problem is that it does does not happen frequently, although this week happened 3 times.sometimes when i have this problem the immobilizer error shows up.it is really a pain since it happens intermittently
 

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Fairly certain a fail to start due to crank position sensor will store a fault code. Read the codes and don't just throw components at it.
 

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If the error code suggests MAF it might be a good idea not to over think things and look at replacing the MAF, especially if you reset the error codes and MAF fault recurrs.
 
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