The test featured in the video is using the O2 sensor at wide open throttle to determine the cause of a low power complaint. This 2000 Mercedes Benz ML320 had very low power (will not go over 20 mph) with random and multiple cylinder misfire codes in memory. In this video I will show you how to prove these symptoms are caused by a lack of fuel, which led us directly to the MAF sensor. I will be showing you MAF data on the scan tool and also detailed testing of the sensor itself using a scope.
You will not need expensive equipment to perform these tests. A basic scan tool that will provide generic data is really all that was needed. The scope stuff at the end is for those of us that cannot test a part enough before we condemn it as being bad.
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium https://www.scannerdanner.com/join-scannerdanner-premium.html There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
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YOU HAVE NO IDEA HOW MUCH THIS HELPED ME, I HAD THE P 300 THROUGH P304 IN THE BEGINNING AND MAF, CLEANED MAF REMOVED THAT CODE, BUT STILL GETTING SURGING WHEN TRYING TO DRIVE , BENCHED TESTED FUEL OXY RATIO SENSOR, 1 VOLT OUT PUT, REPLACED IT AND CAT, WHICH HAD BROKEN LOOSE, HAD TWO TEST DRIVES THINKING IT WAS GOOD,,,, WRONG,,,,,,,,, I HAD FELT THE P300 CODES WERE SECONDARY TO ANOTHER ISSUE REPLACED DOWN STREAM SENSOR, IT WASNT UNTIL I UNHOOKED THE MAF AND HAD AMAZING IMPROVEMENT,, STILL LACKING POWER BUT NO MORE SURGING SLOW STEADY SPEED INCREASE WITH OUT ANY SURGING, JUST YOUR TIP OF DRIVE IT WITH MAF UNPLUGGED DID IT FOR ME, PS WANTED TO BENCH TEST THE VVT SOLENOID,, WHICH CAME APART IN TWO PIECES., I HAVE CIRCLED BACK TO THE MAF , BASED ON DRIVE TEST .
Its not always the MAF if you unplug it and its better. I had the same thing happen recently with the bogging and fuel trims staying high under load. Even had a MAF code. Unplugged the MAF and it ran fine. Ordered MAF. As I was taking it off I realized the accordion style intake boot was so torn up it was like a slinky. So I assume under load it opened up more and instead of showing as a small vacuum leak and being "overpowered" by measured air and correcting it was the opposite.
Took away some confidence because Im not sure how you measure for proper MAF voltage signals now. As in, if you have a large vacuum leak and a working MAF, if you measure MAF signal its going to be rightly low. Dont want to have to bust out the smoked machine for something so basic. Help Danner.
All the diesels that I've owned gave good results in the "unplug it test" in MAF faults. I don't know about gas powered engines, but the diesels did.
same thing my Mercedes is doing
Awesome video……
Very interesting. I think my son is going to try this method as his ML320 barley goes 40 mph! Thank you guys
I use the Calculated Load pid when i am looking at a suspect MAF. I had always used that as a quantifier for how much fuel is being requested by the engine control. Simply put that if the car is on the road and the pedal is mashed then that value should climb high and that the MAF is the main or at least a heavy driver of that number(in most cases)I'm sure there are exceptions but it has been pretty reliable. On a highway I am looking for 85% or greater for a healthy MAF
I learned so much. Thank you! Misbehaving 2006 R350 brought me here.
you beat this mofo to death. Great diagnosis
As always, interesting videos.
What normal figures coming back in a scan tool suggest the mass air filter is lying?
OK V6 ML ,if you have one keep an eye on the temp gauge when they get to hot they like to push the nunber 3 or 6 liner through the head s !
ScannerDanner! You fixed my 1997 Chevy k2500 5.7L vortec. I threw some parts at the truck and never really kept track of what I replaced very well. I bought a cheap $40 map sensor on Ebay which was the cause of the issue. Luckily I kept the old one (never needed to be replaced). Started thinking about the Catalytic converter until I watched this video. I watched my upstream o2 sensors at WOT and sure enough. I installed the original MAF and problem solved. You should travel the states doing some due justice to the diagnostic world of cars/trucks. Think about it, travel paid for through crowd sourcing. Meals taken care of from the people you are doing repairs for (scheduled trip of course). Not too many people like you in this world and that is worth more than you may know. Thanks Danner
when he got back in the car he had the look of a guy who just rocked a massive deuce!
Nice video Paul. I know you have made so far some videos of European car models diagnostics, so I appreciate the effort. And of course I`m not the only one. Keep them coming man! Thanks.
Thank you so much !! This video has just saved me a TON on money on repairs that I did not need !! You ROCK !!
Thank you. This was really helpful.
So how do i get discount on buying your book in PDF format. I want some awesome reading for my holiday on my kobo Linux reader.
Note i am in the UK so there is the exchange rate crap.
I also hate MAF sensors, i prefer a system using a MAP as a bad MAF left unattended can result in engine damage and in many cases you never end up with a code set when they are failing.
Good job guys!
Excellent lesson! Thank you very very much!
I just bought a 2001 Mercedes CLK430 V8 – only has original carfax proving 44000 miles. But been sutting for 2 years. I'm getting a cold for trouble positioning sensor faulty butt I'm getting the same reaction that Mercedes did at full acceleration I'm not picking up speed but I am going over 20mph. question and I know it's hard to answer this question properly I was thinking just to clean out the throttle body and sensor are should I just replace the MAF sensor?
this teacher is retarded, the loud awkward guy that thinks he funny, but really no one can stand, and will never tell the annoying fucker.
Always nice when you can confidently throw a part at it after one test.
That ML has a faulty pulley bearing somewhere in there. Awesome viedo, wish that taught like you do at the tech school i went to years ago.
thank you for posting. I have a customers car with same symptoms. suspected MAFS and tried unplugging with mild improvement. will check my upstream O2 data tomorrow to confirm the fix. – 2006 Nissan Murano. codes were p0171, p0300. stalling/no power. Customer was expecting fuel pump issue.
love your channel
I'm doing a bmwx5 3.0i. ,starts up then immediately starts hunting and spluttering and dies about 8 seconds in and again the scope trace all looks right but it's lean and won't run with the Maf in line in the intake but runs well when connected to the wiring harness but not in the intake pipe (no air passing through ) as on as you put it in the pipe engine cuts at €400 I need to make sure thanks for the vid very very helpful
Yes Sir we do appreciate the good teaching. Paul leaves no stone unturned and is thorough without losing our attention, keeps student involved Thank you P and thanks Rosedale I'm in Ireland so premium is a great way to join in
It's OK, I'm taking a dump why im watching this too