Testing the MAF for dummies

[230K]

Hi

What i did was put pins through each of the wires on the MAF connect and take two wires into the car view the bonnet gap and the front window.
The voltmeter can then be connected to these two wires.

230K

 

[SimonsMerc]

Hi

What i did was put pins through each of the wires on the MAF connect and take two wires into the car view the bonnet gap and the front window.
The voltmeter can then be connected to these two wires.

230K

Oooh, that's clever that is. Means I don't need to beg the wife to hit the accelerator for me! Thanks so much for that, 230K

-simon

 

[Dieselman]

I found it easier to take the ECU plug apart and connect there then used the same technique as 230K.

 

[SimonsMerc]

Ok, well I went out and measured my MAF's voltages and it does seem to be working, but slightly lower than dieselman's results from here.

rpm     volts
 700    1.8 (idle)
1000    2.2
1500    2.5
2000    2.8
2500    3.1
3000    3.4
3500    3.9
4000    4.0
4500    4.1
5000    4.2 (max)

The results are very similar to Dieselman's "New MAF no load" line, although slightly lower at idle and at the top end. Here is a comparison.

rpm     volts     DM's reading
 700    1.8        2.2
1000    2.2        2.3
1500    2.5        2.4
2000    2.8        2.7
2500    3.1        2.9
3000    3.4        3.2
3500    3.9        3.9
4000    4.0        4.3
4500    4.1        4.4
5000    4.2        4.4

Taking into account the human factor (it's bloody hard to keep the counter at x rpm with the gas pedal, and it's even harder to be exact), are these similar enough for me to not be worried about the MAF? Also what did you mean by "no load"? Were you driving at the time you were measuring to get the "under load" figures?

-simon

 

[Dieselman]

These results look Ok for a CDi engined car. The readings are slightly lower because the MAF output is a digital sinal converted to analogue, so the sine wave isn't complete. This makes the DMM read low.

Ahem..I was driving the car to obtain the "load" figures. Obvously had to be in a high gear to load the engine.

 

[SimonsMerc]

These results look Ok for a CDi engined car. The readings are slightly lower because the MAF output is a digital sinal converted to analogue, so the sine wave isn't complete. This makes the DMM read low.

Ahem..I was driving the car to obtain the "load" figures. Obvously had to be in a high gear to load the engine.

Ok great, thanks, that's what I needed to hear. My next stop is going to be a 'tuning box' type thing from tandem tuning on ebay. 230 quid, but if it gets my mpg to a more sane number it'll be worth it!

-simon

 

[peterchurch]

My maf was Fuct from the day I bought my car I had driven loads of SLs but I really did not notice that there was a slight _LAG_ when I reved the car I even got used to driving it with the _LAG_ and I guess I have just been compensating for it over the last few months as it got worse I have had all sorts of diag kit plugged in and nothing showed up I was having some silly random stuff happening so I bought a new Maf on the off chance and BINGO

My thought was sod it! If I buy one and its not the problem at least I have a spare