MAF sensor diagnose

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

Re: MAF sensor diagnose

Post by Pg502 » Fri May 24, 2019 11:41 pm

I have, maybe it measures frequency not voltage

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

Re: MAF sensor diagnose

Post by TechLuke84 » Mon May 27, 2019 6:34 pm

fordsmax471

The MAF uses frequency (Hz) for the signal. You probably have 3 wires for the sensor, ground, 5V reference and signal. You can check power and ground with a multimeter and ignition on but you’ll need an oscilloscope to check the signal at the sensor. What’s the details of the car, symptoms and fault codes?

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

Re: MAF sensor diagnose

Post by Pg502 » Mon May 27, 2019 7:17 pm

Using forscan
At idle
MAF is 4g/sec,
MAF hz around 2000
And increases at a constant rate with higher rpms
It’s 2011 mustang v6 with bbk exhaust system (long tube headers, catted h pipe)
Has an af cold air intake. Previous owner install.

The fuel trims are fine at high rpms
But at idle it’s -14 and goes to positive 12 consistently
And rpms are 600-700 at idle. Shakes a little every 5 seconds at idle
When coming to a stop the car sometimes stalls
Or hesitates dropping to 400rpms and going back to avg 600-700 rpms.
No engine codes
No misfires
Throttle body and pcv are fine

Thanks

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

Re: MAF sensor diagnose

Post by TechLuke84 » Mon May 27, 2019 8:27 pm

Your fuel trim is trying to correct very lean and very rich, have you checked your oxygen sensor readings? Would be interesting to see them.

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

Re: MAF sensor diagnose

Post by Pg502 » Tue May 28, 2019 3:40 am

I ran forscan today
Fuel trims are in -12 and -14
I wasn’t sure what tab is the o2 sensor
But 02s11impe and 02s21impe (sensor impedance is express as voltage )
Was only .09-.10 in voltage
The 02s22 and o2s12 where both alternating voltage between .1 through .8

f-wolf
Posts: 402
Joined: Sat Apr 18, 2015 12:41 am
Vehicle: Ford XR6 Turbo BA MK II 6 Speed Manual

Re: MAF sensor diagnose

Post by f-wolf » Tue May 28, 2019 5:56 am

The O2 Sensors look OK

Try cleaning the MAF sensor with MAF sensor cleaner ...

If No change ... you have to get a new MAF Sensor

https://howtune.com/articles/208-clean- ... ustang

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

Re: MAF sensor diagnose

Post by TechLuke84 » Tue May 28, 2019 7:40 pm

Your oxygen sensors look normal, you can try cleaning the maf but if it doesn’t work I wouldn’t just throw a new one at it! You can check the sensor wiring for a 5V reference and check it has a good ground. Do you have an oscilloscope?

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

Re: MAF sensor diagnose

Post by Pg502 » Tue May 28, 2019 11:40 pm

I tried cleaning the maf sensor, but according to the hz and g/sec of air it seems to be functioning right. I have checked for voltage and ground will a multimeter, I don’t have a Oscilloscope.
The down stream o2 sensors only stay between .09-.1 volts???

f-wolf
Posts: 402
Joined: Sat Apr 18, 2015 12:41 am
Vehicle: Ford XR6 Turbo BA MK II 6 Speed Manual

Re: MAF sensor diagnose

Post by f-wolf » Wed May 29, 2019 4:58 am

The down stream o2 sensors


What voltage should downstream o2 sensor read?

When the air/fuel mixture is balanced or at the equilibrium point of about 14.7 to 1, the sensor will read around 0.45 volts.

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

Re: MAF sensor diagnose

Post by TechLuke84 » Wed May 29, 2019 3:10 pm

Depending on the type of oxygen sensor, they are probably zirconia so the up stream sensors should switch once per second between 0.2v and 0.8v. The downstream will read a steady 0.1v or 0.2v. Expect those readings when the vehicle is in closed loop.

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