Replacement MAF's for the Diesel 75

[wuzerk]

Originally Posted by Bigga

No go under 2k then everything and generally lack of power and just horrible to drive.The only way to test (on mine anyway) is to swap for a known good one or put mine on another car and see what happens, all the best with it anyways.....

Why not just unplug it? If the low speed pickup improves then the Maf is
failing.

[HarryM1BYT]

Originally Posted by wuzerk

Why not just unplug it? If the low speed pickup improves then the Maf is
failing.

Because, as I think we have established, unplugging it is not definitive proof of a bad MAF.

[BigAde]

Think this thread is the right place to post as I'd like the input of HarryM1BYT and Kourgarth among others...

Having originally improved my MAF performance by cleaning it up, it started dropping off again within a week or two.

Seancar tested my MAF at the Polegate meet and couldn't get a reading off it, so it looked like it was knackered.

When I connected Torque Pro up yesterday and measured Mass Air Flow Rate with engine up to tempertaure. The figures I was getting weren't steady though, they fluctuate quite wildly so I couldn't give a clear indication of what the reading is at idle and at 3000rpm. I've also taken a scatter graph of readings and that's all over the place, no nice clear curve as others have posted in other threads.

Today I did the same thing with the engine up to about 85C (it doesn't get to 88C due to top pipe thermostat) and at 780 rpm I got around 12.97 g/s (although it still jumped around a bit above and below this figure). At 3000 rpm I got around 65.0 g/s. So not optimum, but in theory just about withing spec.

When I took my foot off the accelerator and let it drop back to 780 rpm the rate dropped to around 8 g/s for about 30-60 seconds after this before eventually returning to around 12.97 g/s

I've ordered a new £75 Bosch MAF anyway, but would appreciate any input on the existing MAF.

Thanks.

[HarryM1BYT]

Originally Posted by BigAde

Think this thread is the right place to post as I'd like the input of HarryM1BYT and Kourgarth among others...

Thanks.

I am not an expert, I am using a lot of guess work and a lot of common sense.

The value does jump around a lot, as you would expect, it needs to be averaged using a graph, or by guessing. the 30 to 60 seconds seems wrong, but not having a Torque Pro - might it have been averaging and took that long for the average to settle?

[BigRuss]

Originally Posted by BigAde

When I took my foot off the accelerator and let it drop back to 780 rpm the rate dropped to around 8 g/s for about 30-60 seconds after this before eventually returning to around 12.97 g/s

Thanks.

That'll be the EGR opening

Russ

[BigAde]

Thanks Harry & BigRuss, ok if the EGR is the cause I guess that means it might not be the MAF being all over the place. Maybe I didn't need a new MAF after all.

[njb]

mine has the same behavior, maf value dips to 8 g/s when the RPM returns to 780.

Is this normal behaviour?
I fitted new maf last week to try to fix my white smoke on accelerating . I have cleaned egr and replaced pcv.
MPG is poor compared to my last automatic tourer and power seems down.

[HarryM1BYT]

Originally Posted by Bigga

Just to update mine, i read the values using torque, have updated my other post but thought would put on here for others to compare.....

old
800 - 13.2
3000 - 61.3

New
800 - 12.3
3000 - 60.2

Does this mean both mine are knackered? All this maf business confusses me lol

Yes, but only if you are certain there are no other issues.

Only your 3,000 readig is low on the new one. The more the speed of the airflow, the more a restriction will show up. Might that restriction be the filter being dirty?

@780 rpm
MIN - 440mg/st = 11.44 g/s = 1.51 lb/min
OPT - 475mg/st = 12.35 g/s = 1.63 lb/min
MAX - 500mg/st = 13.00 g/s = 1.71 lb/min

@3000 rpm
MIN - 650mg/st = 65.00 g/s = 8.59 lb/min
OPT - 680mg/st = 68.00 g/s = 8.99 lb/min
MAX - 720mg/st = 72.00 g/s = 9.52 lb/min

[Johnny2R]

Measured mine again yesterday and I'm getting 14.2 g/s at 780rpm and 70 g/s at 3000rpm. The 3000rpm is within the good range, but the 780rpm is higher than Harry's max figure. Puzzled by this - it's a new Bosch MAF sensor and my car is running very well with it.

Presumably it is possible, of course, that it is entirely correct, that as a result of something to do with the air intake, it is actually receiving more air at idle than the reference model? A few years ago, when it was fashionable to do so, I cut back the air intake, removing the 'restrictive' section with the bellows. This is now in general thought to be a bad idea and I'm planning to restore it to standard. But in the meantime could this explain the higher figures?

[Retap]

Im posting in this old thread out of appreciation for how useful the info in it is.

My Nigel a ZTT cdti 135+ has been running like a bucket of spanners on and off for over a year and now i am comfortable with TOAF i was able to do some diagnotsics and found the MAF sensor readings problamtic when compared to the chart in the op of this thread. And Turns out i been getting 45mpg all year and thought that was good

Anyway at present Halfrods have what appear to be BOSCH genuine MAF's in at very reasonable price of £154.70.

https://www.halfords.com/car-parts?c...&pid=434750407


I put one in Nigel last week to replace the cheapo one i threw in last year following a limp mode event and its like a new car im back in love with this car lol from low end to high it pulls like a mad man and sounds sweet as and looking forward to my fuel calculations next fill up.


The only thing i noticed is the 3000rpm end air mass measurement is still a bit low below min actually with a new Bosch MAF and wondering if that could be intercooler or turbo seal related, i already have a patch on the intercooler to seal a hole so might be another hole i missed somewhere. already done the large gasket down the bottom of the radiator..... Intend to revisit in a few weeks see how its settled in and weather warmer...