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Lambda sensor which is in the exhaust downpipe is probably faulty, ecu uses it to monitor and adjust combustion mixture (stft, lambda etc. values via obd reader). When you disconect maf the ecu runs "open loop" does not read maf and lambda sensor values and runs
 

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Tangerine Scream ST3 2013, with some stuff done.
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I see you made it over from the US site okay mate, it would be nice if you said hi and introduced yourself, before you jump straight in with a question, this isn’t facetwit you know. 😆
 

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Get a proper diagnosis and codes read before you spend any money on parts. I believe that the car runs open loop until the coolant temperature reaches a certain threshold, it varies between cars but generally it's somewhere between 70C and 80C. Therefore if the car is behaving like this from a cold start it doesn't necessarily point to the O2 sensor being at fault as I don't believe the PCM uses the switching O2 sensor voltage to adjust the fuelling until the car is warmed up.

Also did you replace with a genuine Ford/Volvo (Bosch) MAF or aftermarket?
 

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Discussion Starter · #8 ·
Get a proper diagnosis and codes read before you spend any money on parts. I believe that the car runs open loop until the coolant temperature reaches a certain threshold, it varies between cars but generally it's somewhere between 70C and 80C. Therefore if the car is behaving like this from a cold start it doesn't necessarily point to the O2 sensor being at fault as I don't believe the PCM uses the switching O2 sensor voltage to adjust the fuelling until the car is warmed up.

Also did you replace with a genuine Ford/Volvo (Bosch) MAF or aftermarket?
Yes it was a Bosch I will get it read first and thanks for advice 👍
 

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Tangerine Scream ST3 2013, with some stuff done.
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Map sensors can give some strange problems, might be worth checking, also probably a good idea to check all the boost hoses for splits or loose clamps.
 
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