MAF Replacement

[Timbo_1975]

The ecu takes MAF voltage and converts it to a airflow figure as i said.

The OP basically asked what sort of voltage should he see from the MAF as his truck appeared under powered UNDER LOAD. An OFF LOAD measurment is only an indication that the MAF is capable of giving a sensible figure OFF LOAD, which may well be ~3v.

Andrew appears to be satisifed that a 3v reading will be fine when the turbo is boosting under load. It is NOT.

I have some knowledge of how these systems work given the business that I am in, and can assure you that 4-4.5v is needed for the ecu to apply full fuelling, ESPECIALLY in the mid range 2-3000rpm. You would not believe how many airflow meters we replace that hit an upper limit of voltage at a certain airflow level and limit power.

 

[andrewk]

You guys are missing the point. The workshop manual specifies the voltages at the MAF with the engine hot and in neutral - not my rules about how to measure the MAF but Nissans.

Measuring under load may or may not affect the readings you get, I haven't a clue - but nor have you because you have no reliable source for reference readings measured under load.

Anyone saying that it is necessary or sensible to measure MAF voltages under laod is just flying a kite.

Andrew

 

[BIGSEAN]

"Anyone saying that it is necessary or sensible to measure MAF voltages under laod is just flying a kite."
Have you seen logs from ecutalk Andrew?
Just asking because if you have you would probably realise that they are indeed very relevant to measuring MAF reading ect in context, i.e roadspeed , engine temperature injection timing.
The whole picture can be obtained in real life conditions rather than stationary in a workshop.And as there are no published load figures for MAF readings it is entirely possible to build up your own (as i have) and find that they do indeed corelate with the w/shop figures at the required RPM.
If anybody has any logs they are prepared to share (or if anybody wants a copy of mine)
leave me a message and i will send them.
Perhaps building up our own database will be of benefit to the whole club.

 

[andrewk]

The whole picture can be obtained in real life conditions rather than stationary in a workshop.And as there are no published load figures for MAF readings it is entirely possible to build up your own

For gawd sake, the OP was only asking how to check whether his MAF was goosed or not!! The easiest and quickest way to do that is to follow the process in the workshop manual. You don't need ECUTalk (and all the aggravation that many suffer getting it to work) to do that - just a DVM that you can buy anywhere.

 

[mowerman]

Am I missing something here? I for one do not have ECUtalk/consult or any other fancy programme and laptop to run it on so would have to rely on the workshop manual and a voltmeter also...... so is there a good cheap (not involving expensive pc's & programmes) way we ordinary 'diy'ers can check this sort of thing? Even if I did tape a voltmeter to my wipers and got someone riding shotgun to take readings I dont think I would be the wiser :do:nenau

 

[BIGSEAN]

It is described in the workshop manual how to test your MAF with just a voltmeter
It is a pretty straightforward procedure. There is a link somewhere on here for a download to the manual, unfortunately i cannot find it
Perhaps if you pm Briggie .
Apologies if i have offended anyone, but the whole reason i got Ecutalk was to try and solve my own problems as unfortunately the symptoms my truck was coming up with proved to be any number of possible faults ranging from faulty MAF, Leaky fuel lines, air from fuel filter leaks ect.

 

[andrewk]

so is there a good cheap (not involving expensive pc's & programmes) way we ordinary 'diy'ers can check this sort of thing?

Yes, you need a pen, paper, a bath towel, a pin and a voltmeter of some kind (a DVM or DMM are fine).

Do the following:

1) Find out what colour cable is connected to the MAF output. I assume that those shown earlier in the thread are correct for the 2.7Tdi engine. For a ZD30, it is the red one.

2) Drive the car around until the engine is hot. Lift the bonnet - and use the pin to pierce the cable that is the MAF output. Connect the red DMM probe to the pin and the black one to the battery ground/earth. Partially close the bonnet

3) Fold the towel and put it on the bonnet. Set the DMM to an appropriate range to measure voltages in the range 0-20v and then connect the DMM to its probes. Arrange it on the towel so that you can see it through the window from the driver's seat (the towel just stops vibration shaking it off the bonnet).

4) Turn the ignition on - you should get a reading of about half a volt

5) Start the engine and let it idle. The voltmeter should read somewhere between 1.5v and 2.0v (you can see what mine is from the graphs I posted above) . On very small throttle, increase the engine revs gradually and take readings as you go. MAF output volts should rise as the engine speed rises. It should be somewhere over 3v by the time you get to 3000 rpm.

6) Do not expect the MAF output volts to rise very linearly with engine revs for two reasons. The ECU opens the EGR valve at medium engine speeds and then closes it again about 3200 rpm - which affects inlet manifold pressure. Secondly, the ECU stops the turbo boost pressure rising at about 3200 rpm (coz it knows that there is no load because the throttle opening is small) by either moving the VNT lever (ZD30) or opening the wastegate valve (all the others).

Hope this helps
Andrew

 

[briggie]

page 356 in the ec section ( below ) provides details of the self diagnostic procedure for the mass air flow sensor ( td 27 ) . hope it helps :thumb2

http://bebrs.pie-dabas.net/Webs/Terrano/R20/ec.pdf

 

[TONUP]

By way of an update...

I have followed the process in the download and the are the results...

Prior to removing and cleaning the MAF sensor: -

Ignition off = 1 volt

At tick over = 2 volts

At 3000rpm = 3 volts

At 4000rpm = 3 volts

Following removal and cleaning of MAF: -

Ignition off = 1 volt

At tick over = 2 volts

At 3000rpm = 3 volts

At 4000rpm = 4 volts

Which leads me to believe that the MAF sensor was dirty and not defective. I have taken it for a drive and, allowing for the placebo effect, it does seem better.

Thanks again everybody who contributed to this thread.

Regards

Alan

 

[oorwullie61]

t2 maf

i have a spare new one if you want it for £50 pm me and let me know or phone

 

[Banshee]

Just floating around the forum as I do and came across this gem, look at the tech talk in here boys :naughty

Quite a heated debate too :augie

 

[Mav96]

Hey Clivvy can you find me a Hitachi one for that sort of money please?

https://goo.gl/oapN3z

 

[Banshee]

https://goo.gl/oapN3z

You do realise that he posted that back in 2011 :lol :nenau

 

[Mav96]

You do realise that he posted that back in 2011 :lol :nenau

:doh did not look at dates just noticed the thread was active & jumped straight in without looking as usual, but thats me :lol:lol:lol