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Old 01-05-2017   #76
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Poland 
Re: What could Be Wrong with my Barchetta? Stalling and hectic idle

Thanks for your response eramosa,

My original intent was to replace it, but shouldn't unplugging it be a good test to check if lambda was the cause or not? I expected the ecu to set some kind of richer mixture and bring the idle rpm's a bit higher but make them steady. That did not happen. Or was it because the ecu needs some time adapt? (I kept it running 5 mins on warm idle total).
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Old 01-05-2017   #77
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Portugal 
Re: What could Be Wrong with my Barchetta? Stalling and hectic idle

By unpluging it wille runing should pop out a error code open circuit for the heating element of probe !?
the signal of oxigen level would be 0V interpretated like lean mixture by ECM !!?
also oxigen sensor only works after being hot !
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Last edited by JMSG; 01-05-2017 at 15:28.
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Old 01-05-2017   #78
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Poland 
Re: What could Be Wrong with my Barchetta? Stalling and hectic idle

Okay, I spent couple hours in a garage and I still suspect the o2 sensor.

1. I did some checks on the coils and all seem to easily produce voltage for the spark to jump over ca 15 mm gap in a tester I have. I didn't see any missed sparks. Per the tester setting 15 mm is more than 20kV, so... I think I am good.

2. Then I have finally found an easy way to test if the ICV is not stuck. I noticed it is only possible to see the shaft moving when the motor was assembled with the valve and I was only make this observation when I was looking inside the valve case and through the holes. The motor seem to push the valve shaft by maybe 5 mm when 12V is applied to its pins. I kind of expected it to open more. I have also noticed that when you turn the key the ECU sends ca 4V to it, then when the motor is running cold ECU sends ca 6-7V to achieve 40-50% of ICV full movement. Anyways, I am not sure if I can fully exclude the ICV, but this makes it as a last suspect on the list.

3. Although I was not suspecting it at all I did also check the TPS. The ECU could see the throttle angle change and it was continuous and smooth change. By the way, I have seen something that made me wonder: if I was pressing the pedal to the metal I could only open the throttle by 67% (repeated couple of times) and when I manually pushed on the lever in the engine compartment I could open it by 83%! (repeated as well). Is this normal?

5. Today B. had a good day and after all these checks I connected to ECU and kept monitoring o2 voltage. Since there was barely perceivable vibrations for a moment I thought that maybe I un-stuck the ICV by connecting full 12V to it. When it got warm the o2 voltage was oscillating at 0.4-0.8V I had my fingers crossed, but now and then I saw voltage going down in rapid pikes and then vibrations occured for brief moments. I have increased RPM slightly and after it dropped down to idle lambda voltage dropped too and became 0.3-0.2 with small variations in that range. I think it is either bad or is going bad from time to time (maybe gets too cold = heaters issue). This makes the engine run unstable. What other thing could explain being normal to rich and after adding some gas and going back to idle becoming lean? I have no clue :-). I am thinking about one last check before I spend money on the new sensor: checking the fuel pressure. I am writing this all so that hopefully someone will benefit from it and will be less lost than I am with this issue.

EDIT:

JMSG, as always I appreciate your input. I have assumed that there is an actual difference btw the open circuit and lambda giving 0V. I have seen someone saying that the former makes the ECU assume constant fuel mixture (slightly rich) and the latter cheats the ECU into thinking the mixture is extremely lean. I had hoped I would cause the first situation and this would be my confirmation of the sensor issue. It is funny that actually ECU did not pop up any errors. It may be that I have not waited long enough with unplugged sensor for the engine to get warm and start taking its readings.
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Last edited by MichalM; 01-05-2017 at 21:54. Reason: Needed to added a comment.
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