how to test a MAF

[andy-m]

sometimes when I am off the throttle going down hill for about 20 seconds, the engine check light comes on. if I dip the clutch and let the engine idle momentarily, it goes. Also, under normal driving, when I pull up at the lights, the engine revs momentarily dip lower than normal then return to normal idle, although sometimes it will stay idling slower than it should at about 500rpm unless i blip the throttle.

I have already changed the temperature sensor, the lambda isnt that old and looks to be working fine on my AFR gauge.

I have a spare MAF that I took of my old sscoob before it got scrapped that I was gonna try fitting tomorrow, but before i do, does anyone know how to test a MAF ?
I have a multimeter.

Not sur if you can test a MAFS output with a Meter mate . I'm guessing it must have a nominal output value , but not sure .
Have you plugged the diagnostic connections together under dash to see what fault code is logged .

[andy-m]

i was hoping you wouldnt say that ! couldnt find them last time I looked and I had the lower half of the dash off to make it easier to find too !

I was guessing that the MAF would have a normal resistance range or something as I know the restance of the wire changes with temperature, which itself changes with air flow

[Chris]

The most simple way to test a maf is to unplug it whilst the engine is running.
If the engine dies the mafs ok.
Happy to run a diagnostic for you .
Whereabouts are you?

[andy-m]

crystal palace, so not that close to you. thanks though, i'll unplug it on idle and see what happens and fit the spare if the one in there fails the test

[Chris]

There will be a load of us surrey scoobies lot working on a members car on sat in croydon feel free to drop by if you want us to have a look.

[andy-m]

cheers, may do that (PM me a postcode please for my satnav)

i'll do the unplug test first though, if that doesnt seem to work, i'll pop over

Andy
The plugs for diagnostic are sometimes tricky to spot, they are under the dash pretty much above your knees , part of the main harness .

As said MAF failure will show by unplugging it, although I've had MAF issues where it is failing and not failed completely.

[andy-m]

Originally Posted by Crowman

...although I've had MAF issues where it is failing and not failed completely.

thats what I think is happening to me as the ECL only comes on when I go down a long hill and the low idle sometimes isnt that bad realy.
i'll have another hunt around for those connectors, although that is where I looked last time.

[andy-m]

well found the connectors to check the fault codes and the ECL just stays on.
I checked how to do it propperly, ignition off, connect black plugs, ignition on but not start the engine.
all I get is the ECL staying on. no blinking at all.
may be because the ECU has an Eclipse performance chip replacing the standard chip.

[andy-m]

scratch that, was 24. ICV

Have started a new thread here:-
http://www.southeastscoobies.co.uk/v...061#post136061