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MAF reading

FAQ222

New member
Location
Logan9598!
Car(s)
2008 VW GTI
08 GTI FSI DSG transmission cruising around and can’t tell if the MAF is correct. Translate lbs/min to g/s and 6th gear at 3000 rpm it’s at 3lb/min= 22.67 g/s. The car runs fine but keeps throwing P0238 code. New MAP sensor fixed the car going to limp mode and again it drives fine now except the P0238 “overboost” code.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
A MAF reading at one point in the revs will not give you a reading to know if it is correct. What's there to compare it to? When I look at my previous data for the MAF...I see when cruising at near 3k rpm the data is between 10 and 20 g/s....not able to tell you which gear it was in etc..

What I did is dyno my car to know its HP and which specific gear it was in. Then I can, with a knowingly good/new MAF is, take the max airflow data near redline and divide the data by 0.81 to see if this matches my known HP. So, say its max mass air is 282(g/s) / 0.81 = 348 HP.

You do not need to know the actual HP. You can just check the maximum mass air data with a new MAF and no intake leaks...make note of this for future reference for when you suspect the MAF. Always do the data on the same stretch of road and in the same gear and from a full rev pull to redline. As the max mass air is just prior to redline. I have removed two previous MAFs for seeing data at 248 g/s and 255 g/s. They seem to fade into failure.

OK, moving on to the P0238 code....Typically, people find the P0238 code to be caused by wiring issues because this code refers to the signal the ECU receives from the MAP. Given you replaced the MAP, and it is the correct part, I suggest focusing on the condition of the wires and the connectors to the sensor are in place and connected well and cleanly. How to test the connection between the MAP and ECU is beyond my skill and test data is usually kept for VW tech access...might need further help if it comes to it.
 
Last edited:

FAQ222

New member
Location
Logan9598!
Car(s)
2008 VW GTI
Thanks for the reply. Thanks for the equation on how to figure out how to compare the hp readings I’d never heard of it before.I’m going to dyno the car in 2 weeks and see exactly what’s going on with the car. I have logged quite a few runs this weekend and monitoring what the readings are at various situations like what gear I’m in and what TPS is reading. I’m then having to take those readings and researching on the forums and finding what the readings are supposed to be at. So far I’ve found everything is within 10% of what vehicles with similar mods are logging. Until I can get my boost gauge installed and get it on the dyno I really won’t know if something is off. I’m going to start doing dyno prep maintenance and get the boost gauge installed and probably a wide band of some sort. I hope to get scheduled for the dyno by the end of the month
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Yes, you definitely want to have fresh ignition bits when going in for a tune...unless you are custom tuning it and the tuner includes what they prefer.
 
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