MAF sensor diagnose

Share your FORScan experience with other users
Pg502
Posts: 11
Joined: Sun May 12, 2019 3:18 am
Vehicle: Mustang, v6, 2011

Re: MAF sensor diagnose

Post by Pg502 » Wed May 29, 2019 11:32 pm

All the sensors seem to be working fine.
My long term fuel trim is just low -14.
Could be the aftermarket set up the previous owner added .
Intake and exhaust system ?

TechLuke84
Posts: 31
Joined: Sat Feb 04, 2017 11:19 am
Vehicle: Ford Fiesta Focus Mondeo Kuga

Re: MAF sensor diagnose

Post by TechLuke84 » Thu May 30, 2019 8:00 pm

What’s the long term and short term fuel trims at idle?

Pg502
Posts: 11
Joined: Sun May 12, 2019 3:18 am
Vehicle: Mustang, v6, 2011

Re: MAF sensor diagnose

Post by Pg502 » Fri May 31, 2019 1:11 am

Long term is around -12 -14
And short term -8

Pg502
Posts: 11
Joined: Sun May 12, 2019 3:18 am
Vehicle: Mustang, v6, 2011

Re: MAF sensor diagnose

Post by Pg502 » Fri May 31, 2019 1:36 am

When accelerating the fuel trims are at a low -2,-5

TechLuke84
Posts: 31
Joined: Sat Feb 04, 2017 11:19 am
Vehicle: Ford Fiesta Focus Mondeo Kuga

Re: MAF sensor diagnose

Post by TechLuke84 » Fri May 31, 2019 5:57 am

Your fuel trims should be close to zero but yours are low and in the minus which means the control unit is trying to lean the mixture.

youyoukulude
Posts: 2
Joined: Mon May 20, 2019 3:35 pm
Vehicle: Ford Escort China,1.5L 122ps,L3 2019

Re: MAF sensor diagnose

Post by youyoukulude » Fri May 31, 2019 10:25 am

It's too difficult to understand.

Pg502
Posts: 11
Joined: Sun May 12, 2019 3:18 am
Vehicle: Mustang, v6, 2011

Re: MAF sensor diagnose

Post by Pg502 » Fri May 31, 2019 7:11 pm

Yup it’s crazy,
Thanks guys

TechLuke84
Posts: 31
Joined: Sat Feb 04, 2017 11:19 am
Vehicle: Ford Fiesta Focus Mondeo Kuga

Re: MAF sensor diagnose

Post by TechLuke84 » Sat Jun 01, 2019 7:50 am

Restrictions in air flow intake or exhaust along with fuel injectors dribbling can cause the issue of the control unit lowering the fuel trim into minus figures such as yours. There could be other causes but I’m not with the vehicle to fully see what is going on. The long term fuel trim is memorised by the control unit after seeing the short term fuel trim, your oxygen sensor feedback seems normal which is a little odd, I think it would be good if you reset the keep alive memory and then rechecked the fuel trim and oxygen sensors, this would put the long term fuel trim back to zero and we could see what the oxygen sensors feedback then along with how the control unit reacts with the Short Term fuel trim.

Combustion in engine > Feedback from oxygen sensors > Control unit responds with short term fuel trim > Control remembers and adjusts the long term fuel trim

Hope this helps

TechLuke84
Posts: 31
Joined: Sat Feb 04, 2017 11:19 am
Vehicle: Ford Fiesta Focus Mondeo Kuga

Re: MAF sensor diagnose

Post by TechLuke84 » Sat Jun 01, 2019 7:55 am

To save any confusion when you type -12 -14 you do mean minus 12 and minus 14?

Post Reply