OH MY GOD! What a difference a good MAF makes.....

**sntee** · 14-01-2009,10:36 PM

Just thought I'd post a "quick" recommendation that hopefully might help anyone who's Passat (and possibly other VW Tdi) seems as woefully under powered as mine did.

I was disappointed with my 99 Passat from the moment I bought it, but always put it down to the fact that I still missed my old gas-guzzling Volvo T5

Since then the performance has just got worse and worse. So much so, that a couple of weeks ago I decided that two years of ever increasing misery was enough and if it couldn't be fixed quickly, easily and cheaply, I'd have to sell it and buy something else.

I searched this and other forums for advice but most of the threads I found described the "Limp Mode" problem that seems to affect quite of few of these cars. My problem wasn't as specific or intermittent as that. I just had a significant reduction in power across the entire rev range, in all conditions, regardless of fuel type, road speed, time since last service, etc.

I changed all of the vacuum hoses last weekend and when this had no affect on the problem, I did one last desperate search of the forums and stumbled across a post that mentioned an easy way to check whether the MAF Sensor was functioning correctly.

The advice was to disconnect the wiring connector from the top of the MAF and take the car for a spin. If it drove the same or better, then the MAF was almost certainly faulty.

I followed the advice and..... WOW!!!!

what a difference!!

I immediately ordered a replacement (less than £40 inc shipping for an aftermarket equivalent part) which arrived today.

I fitted it 30 minutes ago and........

WOW!!!!!!!!!!!!

Honestly, the car is at least five times better than when I bought it and a thousand times better than it was this time last week.

So if you think your car is underpowered, please, please, please try disconnecting the MAF, it takes less than 2 minutes, requires no special tools and costs NOTHING!!!!! and it might just save you a whole lot of time and money trying other more complex diagnostics methods.

Sorry to go on, but if this mammoth post helps just one person achieve the same result as i have tonight, it'll be worth the hour that its taken me to write it

**Canetoad** · 15-01-2009,02:13 PM

Do you mean MAF or MAP sensor? They are different.

**sntee** · 15-01-2009,02:29 PM

Definitely MAF (Mass Air Flow)

One other point I forgot to mention is that a duff MAF Sensor won't necessarily throw up any Fault codes in the ECU, so VAGCOM won't find it and it could easily be overlooked by mechanics.

**Crasher** · 15-01-2009,02:37 PM

Do not disconnect the AMM (MAF if you must call it that) unless you can clear the fault code that it will generate doing so. Also, only buy the AMM genuine from your dealer, aftermarket ones last about six months.

**bora(ing) nick** · 15-01-2009,02:43 PM

Originally Posted by Crasher

Do not disconnect the AMM (MAF if you must call it that) unless you can clear the fault code that it will generate doing so. Also, only buy the AMM genuine from your dealer, aftermarket ones last about six months.

Am i right in saying;

AMM - Air Mass Meter
MAF - Mass Air Flow Meter

VAG do not recogneise the term MAF, So AMM is the correct description.

Nick

**Crasher** · 15-01-2009,02:49 PM

Even VAG can’t make up their minds. On the parts system it is an Air Volume Meter and on the workshop system, as Air Mass Meter.

**passat 130 tdi** · 15-01-2009,04:12 PM

will this part make the car chugg slightly at around 30 mph if as not enough revs are being applied ?

**sntee** · 15-01-2009,04:44 PM

I guess so, but don't quote me on that

My car exhibited power loss at all revs / speeds (can't say what it would have been like at 70+ mph cos I could never get there)

Ultimately the MAF, AMM or AVM (3 names 1 part

) tells the ECU how much air is flowing through to the Intake Manifold. This figure is then used in the calculations that decide how much fuel, boost, etc. is required.

Bad AMM = Wrong number to ECU = Engine not performing at optimal parameters

I take Crasher's earlier point about the fault code that will be generated, but would say that the code in itself will not CAUSE any problems and can be easily cleared by anyone with access to VAGCOM or similar, or when the car next goes in for a service (just remember to tell the mechanic that you know why the code is there and its not something that they necessarily need to worry about unless it comes back AFTER they have cleared it)

**hongkongstuey** · 15-01-2009,05:57 PM

mine had a faulty avm/amm when i bought it, didnt realise till i got it serviced and they told me, i didnt know any different, afterwards it was a very different car to drive, then it still had a faulty fuel temp sensor, had to wait for parts and socket to open pump, but it was brilliant after i'd done it, did coinside with getting the car chipped though, so was a million times better after that too!! tiny things of these cars make huge differences in performance