Hi guys, a while back I lost a lot of power in my 1998 TDI beetle. I took out the mass airflow sensor and sprayed it down with electrical cleaner. That made a world of difference. I just feel like I should be getting more power, so I'm looking at buying a new mass air flow sensor. I'm on eBay and see sensors that cost $16 and sensors that cost $90. The $90 one was Bosch and I'm not sure what the cheaper one was, extech or something. anybody have any issues with the cheaper mass airflow sensors? I remember reading something about the cheaper ones not working. Any suggestions on price friendly good brands?
New mass air flow sensor?
- Thread starter Ray299
- Start date
Tdijarhead
Top Post Dawg
- Joined
- Nov 10, 2013
- Location
- Lawrenceville PA
- TDI
- 2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
Never buy a cheap MAF for a vw. Make sure you get a Bosch. Personally I’d get mine from idparts, metalmanparts or another trusted vendor but that’s just me. If you’re sure amazon is selling a genuine bosh MAF and not some repackaged Chinese crap then I guess you’d be good.
Powder Hound
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- Oct 25, 1999
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- Under a Bridge, Crestview, FL, USA
- TDI
- '00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
There are other issues to consider, such as intake clogging if your EGR is still operational.
The best way to decide on whether a new MAF is needed is to log the MAF requested vs MAF actual with a VCDS. The actual should track closely with requested, and if it lags way behind or can't rise above a lower level, then you need a new MAF.
The ghetto way of checking is if you unplug the MAF and it runs better, then get a new MAF.
Good luck and cheers!
PH
The best way to decide on whether a new MAF is needed is to log the MAF requested vs MAF actual with a VCDS. The actual should track closely with requested, and if it lags way behind or can't rise above a lower level, then you need a new MAF.
The ghetto way of checking is if you unplug the MAF and it runs better, then get a new MAF.
Good luck and cheers!
PH
Batmanntexas
Member
What if your actual is higher than your requested? Get a new MAF?
Giberish33
Veteran Member
IIRC that is when the egr is open and recirculating exhaust. They should should track about the same at start up, then after a few min of idle the egr will open up and actual is higher than requested, then egr shuts and they should be about the same again, as Power Hound stated, when they start to go bad/dirt they start to read lower not higher. Here is a thread related to your question:
http://forums.tdiclub.com/showthread.php?t=428917&highlight=idle
Powder Hound
Top Post Dawg
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- Oct 25, 1999
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- Under a Bridge, Crestview, FL, USA
- TDI
- '00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
Nope. When the EGR opens, less air will flow through the MAF. Look at where the MAF is located. It is upstream of the EGR inlet. How could the MAF possibly measure it? Answer: it doesn't. The way the ECU gauges proper MAF flow is to see if the MAF actual drops when the EGR is commanded open. At least, on the ALH it is as simple as that.
Get a VCDS and check a known good car and you'll see this is the case. You can log the MAF while commanding EGR on and off in test mode. You will then see the actual making a definite drop when the EGR is commanded on. A bad MAF will show lower levels all the time, which will not track requested.
Cheers,
PH
Last edited:
Giberish33
Veteran Member
Batmanntexas
Member
So, is there a thought as to why my actual is much higher than commanded? When I bought it, the MAF was bad, it read 189g/s all the time, never changed. I was also getting a code that said MAF was shorted to B+.
I replaced it with a new one, and now my VCDS shows actual is higher than commanded. As far as I can tell, economy is still good, as I average about 47mpg (combined). Having never had a TDI before (and my Camaro has ~800whp), I don't know what 'normal' power for a TDI is, but I feel like it runs 'normal'. I see about 18psi of peak boost on my scan gauge when I am driving it, and I usually try to keep it at 3K rpm, or below, when going through the gears.
Thanks,
Scott
I replaced it with a new one, and now my VCDS shows actual is higher than commanded. As far as I can tell, economy is still good, as I average about 47mpg (combined). Having never had a TDI before (and my Camaro has ~800whp), I don't know what 'normal' power for a TDI is, but I feel like it runs 'normal'. I see about 18psi of peak boost on my scan gauge when I am driving it, and I usually try to keep it at 3K rpm, or below, when going through the gears.
Thanks,
Scott
Powder Hound
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- Joined
- Oct 25, 1999
- Location
- Under a Bridge, Crestview, FL, USA
- TDI
- '00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
Actual higher than commanded is possible if the replacement unit was calibrated for a different engine.
There was a time, way back when Bosch first started out with these new-fangled hot film MAF sensors, that they were failing notoriously. The TDI units weren't quite as bad, but the real tragedy was that VW and Bosch were putting out a crap part and charging the freaking earth for it. I think they should have been charged and convicted. (Note: due to the diesel scandal, looks like many of VW's past sins have caught up with them.)
One of the things tried were MAFs from other makers/applications that fit. I personally tried a Pierburg manufactured unit that was supposed to go in a Mercedes, and it worked very nicely, thank you very much. And yes, the MAF actual showed my engine to suddenly be breathing like a class 8 diesel truck.
In truth, if the air intake plumbing is similar to your current setup, then the proper MAF for that car, if it fits and the pin-outs are the same, will probably get you in the ballpark on air flow. That only works because it is a diesel, for which exact air-fuel ratio isn't quite as critical as for a gasser, since perfectly stoichiometric ratios aren't required. Diesels do normally run excessively lean. Usually.
By now, the MAF problems are mostly solved, and the exact MAF will be available from legitimate sources rather than substandard chinesium units from fleabay. Good luck!
Cheers,
PH
There was a time, way back when Bosch first started out with these new-fangled hot film MAF sensors, that they were failing notoriously. The TDI units weren't quite as bad, but the real tragedy was that VW and Bosch were putting out a crap part and charging the freaking earth for it. I think they should have been charged and convicted. (Note: due to the diesel scandal, looks like many of VW's past sins have caught up with them.)
One of the things tried were MAFs from other makers/applications that fit. I personally tried a Pierburg manufactured unit that was supposed to go in a Mercedes, and it worked very nicely, thank you very much. And yes, the MAF actual showed my engine to suddenly be breathing like a class 8 diesel truck.
In truth, if the air intake plumbing is similar to your current setup, then the proper MAF for that car, if it fits and the pin-outs are the same, will probably get you in the ballpark on air flow. That only works because it is a diesel, for which exact air-fuel ratio isn't quite as critical as for a gasser, since perfectly stoichiometric ratios aren't required. Diesels do normally run excessively lean. Usually.
By now, the MAF problems are mostly solved, and the exact MAF will be available from legitimate sources rather than substandard chinesium units from fleabay. Good luck!
Cheers,
PH