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MAF reading too high

19K views 28 replies 5 participants last post by  Justinlw 
#1 ·
Hi guys. I'm kinda new to this forum. but like all people I am looking for some advice/information. My MAF sensor is maxing out at 600.0 at three-quarter throttle, and it's building boost to about 38 psi on an IDP tow tune while towing a 12,000 lbs trailer but it feels low on power. My brothers 6.4 MAF only goes up to 350 on a performance tune at wide open throttle. Any ideas??
 
#2 ·
Have you tried cleaning it? Mine tends to max out as well but it hasn't been an issue as of yet. Are you reading the sensor with the same monitor on both trucks? The minimax and cts both read the sensor but both use completely different measurements.
 
#3 ·
Yes I used the same reader, cleaned the sensor already and even swapped the MAF sensor from one truck to the other. My truck still maxes the MAF sensor out at 600.0 as to my brothers truck still maxes out at 350 to 380 so I know it's not the MAF sensor.
 
#4 ·
Does one truck have a cai and the other have the stock filter???
 
#6 ·
Mine will max out with decent throttle input but it hasn't caused any over boost problems. Watch map and ebp as well... What monitor are you using?

What is your ebp reading with koeo and koer?
 
#8 ·
Stupid idea I am sure, but have you considered swapping MAF sensors and seeing what you get? If nothing changes, there has to be something further down the line. When was the last time the filter was changed and with what brand?
 
#10 ·
Just from the little looking into things there are a lot of threads linking bad injectors to high MAF values. I know enough to be brave enough to tear into things, but am willing to be more than happy to admit I am no tech.

What computer takes in/reads the values from the MAF? Could it be an issue there?

Can I have the DTC??
 
#12 ·
Other questions are what values do you get when you return the truck to stock?

Excuse my inexperience but the output for the MAF is in volts, right? And so many lbs/min in air flow? What value are you saying is 600 vs 3__? I like to dig deep into this stuff so if it happens to me, I know what to do, plus help others if needed. It sure appears like a low MAF reading is far more common than a high.
 
#14 ·
Well that throws a wrench in things. Have you tried to pull codes with a different reader?

I have seen issues over and over again with collapsed or cheap filter. There are just too any 'possibilities' and I really hope someone will get you the help and fix you need.
 
#15 ·
Guys I'm going nuts here. Anybody what normal readings are for MAF, MAP, EBP, at idle. Trying to figure out if one of them is shot. I have cleaned them all and for the MAF I'm getting around 138-150 g/s, MAP is at 15 psi and EBP is at 2 does this sound right?
 
#20 ·
Ok right off the bat I noticed your MAP reading is higher then your EBP reading.....With truck running your EBP should read slightly higher then your MAP reading. Now whether it's your MAP sensor or EBP sensor that is wrong is the question. With truck off re check the readings and whichever one reads the same as atmospheric pressure for your area is the right one I would guess.
 
#17 ·
From everything I am reading all of these sensors have an effect on the VGT vanes. How did you clean the sensors? The MAF sensor I am guessing isn't your issue since you swapped them on the trucks on you're getting the same reading unless there's a short in the harness somewhere coming from the MAF (it appears to be a common issue that the pigtail to the MAF wears,chaffs, and then shorts). If the EBP and tube are clean, then that should rule that out. It's crazy that there aren't any codes considering that the PCM should read a high output...I have no idea if the information I found will help, but this is what I found thus far.

MAF: Mass Air Flow (MAF) Sensor

The MAF sensor provides a signal to the PCM proportional to the intake air mass. The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. The hot wire is maintained at a constant temperature above ambient. Air passing over the hot wire cools the wire. The current required to maintain the temperature of the hot wire is proportional to the air flow.

The MAF sensor is a digital sensor that provides an output signal of varying frequency. The signal's time period is proportional to the flow rate crossing the sensor. The greater the air flow the greater the time period. The time period varies from 130 microseconds (15 kHz) at a low flow or idle condition, to 530 microseconds (1.9 kHz) at a high flow rate condition. If the sensor element is broken the diagnostic mode default output of the sensor will be 4650 microseconds (215 Hz).

MAP:
Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a voltage signal to the PCM relative to the intake manifold pressure. The sensor voltage increases as the pressure increases. The MAP sensor allows the PCM to determine the engine boost to calculate fuel quantity. In addition, the MAP signal is used to control smoke by limiting fuel quantity during acceleration until a specified boost pressure is obtained, and is used by the PCM for EGR system calculations and control.

A MAP signal concern (an incorrect signal from the MAP sensor), when detected by the PCM, results in the PCM using an estimated, calculated manifold pressure that is derived from known engine conditions in place of the signal from the sensor.

An open or short in the MAP sensor wiring results in an out of range high or low voltage, at the PCM.

The output of the sensor ranges from 0.175 volts at 28.6 kPa (4.15 psi) to 4.825 volts at 616.5 kPa (89.42 psi). At an atmospheric pressure of 101 kPa (14.65 psi) the output of the sensor is between 0.67 and 0.82 volt.

EBP-This was as close as I could find...
Exhaust Pressure (EP) Sensor

The EP sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a linear analog voltage signal that indicates pressure. The sensor voltage input to the PCM increases as the pressure increases. The EP sensor, located at the left rear of the engine, measures the pressure in the exhaust manifold. The sensor feedback signal is used for variable turbocharger geometry and EGR valve control.

An open or short in the EP sensor wiring results in an out-of-range high or low voltage, at the PCM.

The output of the sensor ranges from 0.175 volt at 28.6 kPa (4.15 psi) to 4.825 volts at 616.5 kPa (89.42 psi). At an atmospheric pressure of 101 kPa (14.65 psi) the output of the sensor is between 0.67 and 0.82 volt.
 
#18 ·
Big question here... is the number your concern or are you getting an overboost/underboost concern?

If not then your problem may lie deeper than the sensor. Or... It may be nothing. I will get numbers for you tonight on my way home from work (its going to be a few hours, doing an overnight :( ).
 
#23 ·
Ahh ok....Mine doesn't account for atmospheric pressure........Would that not mean that the Edge insight would also account for atmospheric pressure for the Map sensor reading as well then? Mind you if it doesn't then your readings still may not be far off as mine reads 14 n change for the Map at idle and 16 n change for the EBP so roughly a difference of 2 psi give or take. So if the Edge doesn't compensate for atmospheric pressure...then a MAP reading of 15 would be close to what mine reads with the normal 2 psi difference give or take.
 
#22 ·
Side note... Check your baro reading as well.

When the truck overboosts whats your back pressure look like? At 20psi ebp is usually 25-27psi for me. MAF will max at around half throttle on my truck. Once I hit 30psi boost ebp is usually about 35ish. It also depends on what load is actually on the motor (on a hill, going down hill, towing, etc...).
 
#26 ·
I'm running H&S now, and the issue is causing high egt and smoke at low rpm since switching to a S364.5 Single. The sequentials cleaned it up before, so I never really worried about it.

High MAF reading remains on sct and H&S. Around 150g/s at idle, and maxed at 600g/s cruising.
 
#29 ·
Can you post what your MAF numbers look like at idle and cruising?
 
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