mass air flow sensor question

[93corradoguy 0]

Is there a way to test your mass air flow sensor?

[TIMMYVR 0]

Have a look through the topics on airflow meters mate, im sure there is a way of checking it. It should do certain things when its disconnected whilst running, but have a look cause i know its covered here somewhere.

[Petros 0]

I asked this in this a different thread the other day. According to dr_mat, who certainly sounds like he knows his stuff:

 

There's no easy test, you have to use a test rig and an oscilloscope or accurate voltmeter to see if it's within calibrated range at each fluid flow rate.

 

But they often show up on ebay from cars that are being broken. Get one cheap. It doesn't really matter if it's 100% or not, just *any* improvement in behaviour tells you your original one was probably not working right.

[dinkus 10]

Er, the easy test is to start the engine and unplug the MAF.

 

If the engine coughs and splutters and most likely, stalls then the MAF is working - how well it's working is another matter tho.

 

Just plug it back in and re-start the engine and you'll be ok again.

 

If nothing happens then the engine's already coping with having no MAF and it's buggered.

 

I'm fairly sure that test works for all VR Corrados, but I heard that it doesn't on some of the later, possibly OBD II VRs that were in the Goofs.

 

Have a search for "MAF AND test" and see what crops up :)

[Kevin Bacon 5]

The 4 pin MAF ECUs (OBD2 and OBD1 95>) will just stall out instantly if you pull the MAF. But on OBD2 you can pull of Air mass readings from VAG com, you can't on OBD1 of any revision, unfortunately.

 

OBD1 5 pin 'wire' MAFs will stall out if the MAF is OK. If the MAF is dead, or has a signal the ECU doesn't especially like, it will have already been bypassed by the ECU (TPS is the substitute sensor) and pulling it will have no effect on the idle.

 

Other than that, the only way to test a MAF is to check it's output signal on an Oscilliscope, but even then it's inconclusive as some cars still don't run right on a seemingly perfect MAF!! Weird science!

[Skimask 0]

Corrado guy - try the attached DOC file. I'm not sure if it'll help. As stated previously the general test for a MAF is to disconnect it when running see if it makes a difference. The Corrado ones seem to be more complex though.

By the way - my MAF is knacked unplugging it makes no difference - I'm gonna try the electrical tests outlined in the file just to see the results

[dr_mat 0]

Alright, once AGAIN I'm going to point out that my '95 VR6 with a 4-pin MAF and an OBD1 ECU does NOT STALL when you disconnect the MAF at idle. And that is with a new MAF, which I know is working. The "stall test" is not conclusive. (And this isn't just me that says this.)

 

The big problem with the MAF is that it's job is to measure flow rates in a turbulent fluid. Tricky. But if you take it to bosch there's a test rig. Push a fixed flow rate past it, measure the output voltage. If it's to spec, tick the box, move on. (Minor variations will be adapted to by the ECU anyway.)

 

That said, one way to test the MAF is to disconnect it and attempt to rev the engine. The idle may not be altered, but you'll sure as hell find the car doesn't want to rev and chokes every time you touch the throttle. If it revs like normal with the MAF disconnected, then the ECU is ignoring it and it's time to get a new one.

 

Other than that, your only real option (unless you happen to work for a Bosch test shop) is to try another one and see if the car drives better.

 

*** -- the above document is quite cool. You just have to figure out a way to leave the multiplug connected and tap off these voltage readings. The pros have intermediate connectors with t-pieces.