Maf 101

[celry]

I was able to get it to 5000 earlier this evening, no problem with a cool engine in neutral. Thanks!

 

[bam_bam_dip]

Yeah, I've had mixed results at times wwith the redline test. But its just 1 piece of a puzzle.

Get those logs!!

 

[BioBob]

MAF at idle

I hooked up my Vag-com yesterday, and did an engine test.

The only odd thing I saw was this:

MAF spec 270 --- MAF Act 485.

After reading MAF101, I am concluding that I am getting too much air-flow.

Am I on the right track here, and is this a problem?

Thanking you in advance.
Bob

 

[rdkern]

MAF test is a WOT run from 2K to 4K in 2nd, 3rd, and if room (legally,safely) 4th. You should get requested at 800, and actual over 1000. Don't worry about the "too much" air at that one-shot level.

 

[Wingnut]

I hooked up my Vag-com yesterday, and did an engine test.

The only odd thing I saw was this:

MAF spec 270 --- MAF Act 485.

After reading MAF101, I am concluding that I am getting too much air-flow.

Am I on the right track here, and is this a problem?

Thanking you in advance.
Bob

Blip the accel pedal. If the car has been indling for more than a minute or two, the EGR will close, thus showing the actual reading at 485. If you blip the accel pedal, the EGR opens again and the actual MAF reading goes down (because air is bypassing the MAF and going into the intake through the EGR). Any time the actual is bigger than the requested, thats a good thing. Its when the actual readings are lower than the requested that you need to worry about changing it out. And as the previous poster mentioned, the test has to be done under load. A bad MAF might not show itself under normal driving conditions. You need to tget the requested up to 800mg/r and see what the actual is reading to determine if you need a MAF or not.

 

[bam_bam_dip]

http://www.myturbodiesel.com/1000q_how_to/a4/maf.htm

Copycats.............

A form of flattery, I guess.

 

[chittychittybangbang]

Well I did give "bam bam dip" credit on the picture with a watermark! If you have any suggestions I am always available to edit/correct it or remove pictures that can be credited to you that you wish.

http://www.myturbodiesel.com/1000q_how_to/multi/MAFfaq.htm
A more general FAQ on the mk3, mk4, mk5 MAF w/clickable part numbers to worldimpex for the MAF and metalnerd for the MAF removal tool.

Every writeup on the site also follows a standard format (introduction, parts, procedure).

.

 

[G60ING]

I had a sudden loss of power and the car revved like my G60 Corrado when the cat was clogged. slow to rev. The tdi would boost no higher the 12-14 psi and very slowly. So I figured a MAF. After scanning the car when I found a code for implausible signal for the MAF after arriving home. Has anybody else gotten this? I plan o confirm the reading by unplugging the MAF to see if performance improves.

 

[bam_bam_dip]

Could be just the connector, or the MAF suddenly went south. I bet you will figure it out shortly.
Try reseating the connector a few times, maybe give it a good cleaning. Then give it a test run. If that doesn't work, definately try unplugging it.

 

[G60ING]

I tested it this morning and performance unplugged was no better then plugged in. But Vag-Com threw 2 codes with it unplugged versus the single code when it was plugged in.

A Peirburg MAF has been ordered.

 

[KKennedy]

MAF Implausible Signal

Thanks for this thread.

My 03 Jetta ALH has 209,000 on it and I've just experienced the loss of power. Upon starting, the engine won't rev above 2k rpm unless I go down a hill. This seems to "help" the engine to rev over 2k. After this, the engine runs normally until I shut it off.

I ran VAG-COM and got:

2 Faults Found:
16485 - Mass Air Flow Sensor (G70): Implausible Signal
P0101 - 35-00 - -
16786 - EGR System: Excessive Flow
P0402 - 35-10 - - - Intermittent
Readiness: 1 2 0 0 0

When I disconnect the MAF sensor, the engine runs fine.

Does this mean the MAF is dead?
Should I even try to clean it since I've so many miles?

I don't know what to make of the self correction after I get it going down a hill.

I'd appreciate any advice.

 

[paramedick]

Order a MAF. At your mileage, it doesn't owe you a thing.

 

[TornadoRed]

Does this mean the MAF is dead?
Should I even try to clean it since I've so many miles?

I don't know what to make of the self correction after I get it going down a hill.

VAG-COM doesn't lie -- you need a new MAF sensor.

Also, if you haven't replaced your air filter in the last 40k miles, then it would be a good idea to do that before or at the same time. You wouldn't want your new MAF sensor to get contaminated by dirty air, if there's any leakage through or past the air filter.

 

[dausone]

Am I missing something here?

I removed the MAF from my 03 Golf and this is what I found... doesnt look anything like the part recommended for my year on Impex. Plus the part number on my MAF is Bosch F 00C 262 056. In my repair manual there is an image of the exact same MAF but I have yet to find one that looks similar online. Anyone care to help a confused TDI'er out?

 

[paramedick]

When you buy a new MAF, you get the part pictured and the housing it's mounted into. Just remove the two screws securing it to the air filter housing, and pop the new assembly in.

 

[dausone]

Doh! I see I see... its all so clear to me now.

Thanks for the insight paramedick.

 

[Dimitri16V]

I had a sudden loss of power and the car revved like my G60 Corrado when the cat was clogged. slow to rev. The tdi would boost no higher the 12-14 psi and very slowly. So I figured a MAF. After scanning the car when I found a code for implausible signal for the MAF after arriving home. Has anybody else gotten this? I plan o confirm the reading by unplugging the MAF to see if performance improves.

That's because you went to limp mode. if you get the error again after erasing it, try cleaning the MAF and try again. I gotten this error once, deleted it and never came back.

IF YOU HAVE A PD , THE MAF IS DIFFERENT THAN THE ALH ONE . ALHs MAF WILL WORK ON A PD BUT IT WILL SMOKE TOO MUCH

 

[BoostdJetta]

Just to add my $.02, I had what I thought was an unsual MAF failure. Right before I bought my car the P/O bought a new one... it was clearly bad when I got the car (absolutely no power)... so I bought a new Pierburg unit. It acted differently out of the box than what I had expected but since I never experienced the car with a truly good MAF... it would stumble at idle when letting the clutch out (only when the car was cold), it had a weak spot in the power band at 1800rpms, and it would cause the car to smoke like a freight train over 3k. I hooked my VAG-COM up and noticed the 'actual' reading was acting strange right at those same RPMs... I got ahold of the vendor (BleachBora) who gladly stood behind his part... and now I have a new Bosch unit which is working great with the car running the best it ever has.

 

[Franko6]

CRC MAF cleaner = starting fluid

http://www.crcindustries.com/auto/content/prod_detail.aspx?S=Y&PN=05110

I got some at PEP Boys.

Someone I know had some of this in their 'box of goodies' in the trunk... $5 a can... I think that is what you call marketing... it's a $2.50 can of starter fluid...

 

[G60ING]

That's because you went to limp mode. if you get the error again after erasing it, try cleaning the MAF and try again. I gotten this error once, deleted it and never came back.

Clearing the code did NOTHING. Spraying contact cleaner did NOTHING.

REPLACING the MAF REPAIRED the problem.

 

[KKennedy]

New MAF but weak power

I replaced the MAF with the new BOSCH part purchased from TDIparts. I also replaced the airfilter and performed the Cage mod. I connected VAG-
COM and cleared the codes. They haven't come back after a couple of test drives. I looked at MAF specified versus MAF actual using VAG-Scope. Not really sure what this tells me. I noticed that the MAF actual will spike if I tap the throttle but the MAF specified just stays flat.

It still seems that the engine just won't turn up the RPMs like it used to. I know several of you have recommended cleaning the intake/EGR. My question is: how do I use VAG-COM to make sure my turbo is healthy. I've downloaded the latest version (704) and run through all the measurement groups but none seem to measure turbo performance.

Any advice would be appreciated. Thanks.

 

[vwlogue]

MAF should be at or above 850 at 3000 RPM during a pedal to the metal pull from 2000 to 3500 RPM in 4th.

MAP (block 11) can be logged at the same time, and would give you a picture of the turbo boost and VNT. See the OBD-scanner forum for some posting regarding VAG-COM logging.

 

[KKennedy]

New MAF weak power

Thanks vwlogue for responding so quickly. I ran a road test and logged blocks 11 and 3. It took me a while to get the car up to 3k RPM. Wow that log feature is cool! Never used it before. It shows a reading at 3003 RPM for MAF specified = 805 and MAF actual = 455 (Block 3). It shows MAP specified = 1948.2 and MAP actual = 1050.6 (Block 11).
My interpretation is that MAF is way too low and my turbo isn't performing to specification.
Could you offer advice on further diagnosis or repair? Thanks again.

 

[bam_bam_dip]

Post logs of MAF. It should easily clear 1000. If it is flatlined at 850, then it is no good.

 

[KKennedy]

Friday 7 December 2007 10:49:35
038 906 012 GN 1.9l R4 EDC G000SG 4308
Group A: '011 Group B: '003
Engine speed Specified MAP Actual MAP D.cycle MAP v. Engine speed MAF (specified) MAF (actual) EGR duty cycle
TIME rpm 1850-1950 mbar 1700-2080 mbar 45-95% TIME 870-950 rpm 230-370 mg/H 230-370 mg/H 40-75%
Marker STAMP /min mbar mbar % STAMP /min mg/str mg/str %
0.32 1491 1111.8 938.4 92.4 0.01 1512 385 435 84.1
0.96 1491 1111.8 948.6 92.4 0.64 1512 425 430 82.5
1.62 1827 999.6 928.2 92.4 1.29 1386 250 470 84.5
2.26 2121 1723.8 938.4 92.4 1.94 2205 610 460 19.9
2.9 2163 1948.2 989.4 92.4 2.58 2142 745 485 4.8
3.54 2247 1948.2 1009.8 92.4 3.22 2205 775 500 4.8
4.18 2310 1948.2 1009.8 92.4 3.86 2268 775 490 4.8
4.82 2373 1948.2 1009.8 92.4 4.5 2331 775 500 4.8
5.46 2436 1948.2 1009.8 92.4 5.14 2394 780 495 4.8
6.1 2247 1009.8 999.6 92.4 5.78 2478 765 485 4.8
6.74 1785 1866.6 989.4 92.4 6.42 1932 675 495 19.9
7.38 1806 1887 999.6 92.4 7.06 1806 765 475 4.8
8.02 1848 1907.4 1009.8 92.4 7.7 1848 770 475 4.8
8.66 1890 1927.8 1009.8 92.4 8.34 1890 770 480 4.8
9.3 1932 1948.2 1009.8 92.4 8.98 1932 765 480 4.8
9.94 1974 1948.2 1009.8 92.4 9.62 1953 765 500 4.8
10.58 2016 1948.2 1020 92.4 10.26 1995 755 495 4.8
11.22 2037 1948.2 1020 92.4 10.9 2016 755 500 4.8
11.86 2079 1948.2 1020 92.4 11.54 2058 750 515 4.8
12.5 2100 1938 1020 92.4 12.18 2079 745 495 4.8
13.14 2121 1948.2 1020 92.4 12.82 2100 715 500 4.8
13.78 2142 1948.2 1020 92.4 13.46 2121 795 500 4.8
14.42 2163 1948.2 1020 92.4 14.1 2142 795 500 4.8
15.06 2184 1948.2 1020 92.4 14.74 2184 795 495 4.8
15.7 2184 1948.2 1020 92.4 15.38 2184 795 500 4.8
16.34 2205 1948.2 1020 92.4 16.02 2205 800 490 4.8
16.98 2226 1948.2 1020 92.4 16.66 2226 800 500 4.8
17.62 2205 1948.2 1020 92.4 17.3 2226 800 495 4.8
18.26 2163 1948.2 1020 92.4 17.94 2184 795 500 4.8
18.9 2142 1948.2 1020 92.4 18.58 2163 795 500 4.8
19.54 2121 1948.2 1030.2 92.4 19.22 2121 795 490 4.8
20.18 2100 1948.2 1030.2 92.4 19.86 2100 795 500 4.8
20.82 2079 1948.2 1030.2 92.4 20.5 2079 795 500 4.8
21.46 2058 1948.2 1030.2 92.4 21.14 2058 795 495 4.8
22.1 2037 1948.2 1030.2 92.4 21.78 2058 795 495 4.8
22.74 2037 1948.2 1030.2 92.4 22.42 2037 795 500 4.8
23.38 2037 1101.6 1030.2 92.4 23.06 2037 795 500 4.8
24.02 2016 1948.2 979.2 92.4 23.7 2016 575 460 73.7
24.66 1953 999.6 958.8 92.4 24.34 1974 275 460 78.9
25.3 1869 999.6 928.2 92.4 24.98 1911 275 440 84.5
25.94 1827 1744.2 928.2 92.4 25.62 1827 300 435 84.5
26.58 1827 1897.2 969 92.4 26.26 1827 795 455 4.8
27.22 1827 1897.2 999.6 92.4 26.89 1827 795 465 4.8
27.85 1848 1897.2 999.6 92.4 27.53 1848 795 470 4.8
28.49 1869 1917.6 999.6 92.4 28.17 1848 795 460 4.8
29.13 1869 1917.6 1009.8 92.4 28.82 1869 795 470 4.8
29.77 1869 1917.6 1009.8 92.4 29.45 1869 795 475 4.8
30.41 1869 1917.6 1009.8 92.4 30.09 1869 795 460 4.8
31.05 1890 1917.6 1009.8 92.4 30.73 1890 795 470 4.8
31.69 1890 1927.8 1009.8 92.4 31.37 1890 795 475 4.8
32.33 1911 1938 1009.8 92.4 32.01 1890 795 490 4.8
32.97 1911 1948.2 1009.8 92.4 32.65 1911 795 470 4.8
33.61 1953 1948.2 1009.8 92.4 33.29 1932 795 480 4.8
34.25 1953 1948.2 1009.8 92.4 33.93 1953 795 475 4.8
34.89 1932 999.6 989.4 92.4 34.57 1953 595 480 4.8
35.53 1869 999.6 938.4 92.4 35.21 1911 275 425 84.1
Friday 7 December 2007 11:04:00
038 906 012 GN 1.9l R4 EDC G000SG 4308
Group A: '011 Group B: '003
Engine speed Specified MAP Actual MAP D.cycle MAP v. Engine speed MAF (specified) MAF (actual) EGR duty cycle
TIME rpm 1850-1950 mbar 1700-2080 mbar 45-95% TIME 870-950 rpm 230-370 mg/H 230-370 mg/H 40-75%
Marker STAMP /min mbar mbar % STAMP /min mg/str mg/str %
0.59 2667 1224 989.4 92.4 0.27 2646 460 455 29.1
1.23 2688 1234.2 989.4 92.4 0.91 2667 475 445 25.9
1.87 2709 1234.2 989.4 92.4 1.55 2709 475 455 19.9
2.51 2751 1346.4 989.4 92.4 2.19 2730 480 455 19.9
3.15 2793 1570.8 1040.4 92.4 2.83 2772 670 465 19.9
3.79 2814 1540.2 1050.6 92.4 3.47 2814 680 480 19.9
4.43 2856 1550.4 1060.8 92.4 4.11 2835 675 480 19.9
5.07 2877 1601.4 1060.8 92.4 4.75 2877 680 490 19.9
5.71 2898 1652.4 1050.6 92.4 5.39 2877 710 475 19.9
6.35 2919 1897.2 1050.6 92.4 6.03 2898 765 475 4.8
6.99 2919 1948.2 1050.6 92.4 6.67 2919 795 470 4.8
7.63 2919 1326 1050.6 92.4 7.31 2919 745 470 4.8
8.27 2919 1397.4 1040.4 92.4 7.95 2919 535 470 19.9
8.91 2919 1683 1050.6 92.4 8.59 2919 665 475 19.9
9.55 2919 1713.6 1050.6 92.4 9.23 2919 735 470 19.9
10.19 2919 1948.2 1050.6 92.4 9.87 2919 770 470 4.8
10.83 2919 1948.2 1050.6 92.4 10.51 2919 805 465 4.8
11.47 2919 1948.2 1050.6 92.4 11.15 2919 805 460 4.8
12.11 2940 1948.2 1050.6 92.4 11.79 2919 805 465 4.8
12.75 2940 1948.2 1040.4 92.4 12.43 2940 805 465 4.8
13.39 2961 1948.2 1050.6 92.4 13.07 2961 805 460 4.8
14.03 2982 1948.2 1050.6 92.4 13.71 2961 805 455 4.8
14.67 3003 1948.2 1050.6 92.4 14.35 2982 805 470 4.8
15.31 3024 1948.2 1050.6 92.4 14.99 3003 805 455 4.8
15.95 3045 1948.2 1050.6 92.4 15.63 3024 805 460 4.8
16.59 3066 1948.2 1050.6 92.4 16.27 3045 805 450 4.8
17.23 3066 1948.2 1050.6 92.4 16.91 3066 805 465 4.8
17.87 3087 1948.2 1050.6 92.4 17.55 3087 805 460 4.8
18.51 3108 1948.2 1050.6 92.4 18.19 3108 805 455 4.8
19.15 3129 1948.2 1050.6 92.4 18.83 3129 810 465 4.8
19.79 3129 1948.2 1050.6 92.4 19.47 3129 810 450 4.8
20.43 3150 1050.6 1050.6 92.4 20.11 3150 810 455 4.8
21.07 2436 1009.8 969 92.4 20.75 2835 300 430 63
21.71 2394 1009.8 938.4 92.4 21.39 2331 275 420 84.5
22.35 2373 1009.8 928.2 92.4 22.03 2373 280 420 84.5
22.99 2310 1009.8 928.2 92.4 22.67 2352 280 420 84.5
23.63 2205 999.6 928.2 92.4 23.31 2268 275 435 84.5
24.27 2100 999.6 928.2 92.4 23.95 2163 275 425 84.5
24.91 2016 999.6 938.4 92.4 24.59 2058 275 425 84.5
25.55 1911 999.6 938.4 92.4 25.23 1953 275 425 84.5

 

[bam_bam_dip]

Can you put the data in excel? If not, email me the file, and I'll do it for you.

If you can get it in excel, you can graph it easily. It should look like this...

The first romp goes well over 4000 rpm, then as is wants to upshift........limp mode. The second romp was in limp mode.

 

[vwlogue]

Put the RPM as the X-axis for easier reading; http://forums.tdiclub.com/showpost.php?p=1946842&postcount=17

 

[bam_bam_dip]

Your MAF looks flatlined to me. Contact the vendor and see what they wil do about replacement.

 

[mchabot]

I wanted to have you guys take a look at this reading. Notice that as engine RPMs climb the MAF actual drops below specified. Do I have a MAF that is on its way out?

 

[rdkern]

I'll chime in with my misunderstanding.

This is an A4 - so the spike seems normal. This is chipped? I'd guess so since the "averaging" seems above requested. But not much. I'm confused by 36 seconds-38. Where was the pedal then?

Looks good to me. I wouldn't bother it unless there was a performance reason that you're not happy with. In which case, I'd start elsewhere.