Confirm faulty MAF please?

[r44flyer]

Hello all,

I have recently bought a new Bosch MAF from the popular German seller on ebay. This was fitted when I removed a Synergy/Pierburg combo. I have since become convinced that whilst the performance without the Synergy is obviously very different, the pick up under 2000rpm is surely not as good as it should be in standard form.

So, today I unplugged the MAF and did a back to back test of acceleration in different gears at different speeds. The performance between 1000 and 2200 or so is much better with the MAF disconnected. It redlines just fine. There's no significant smoke. The EGR is surprisingly clean.

I suspect the MAF is out of spec, despite being brand new. Does everyone agree?

[tdi90]

If its the same seller I got mine from in Germany (recommended from here), then yes. Mine failed after about 6 - 7 ish months. Like an idiot though, I took out the MAF insert and fitted it to my original housing therefore invalidating my warranty :getmecoat:

BUT I ordered 2. 1 for me and 1 for a friend and his is still working 100% so reckon I musta been unlucky :shrug:

[r44flyer]

I damaged the corner of the warranty sticker when fitting it, so I wonder how picky they will be on that. It certainly hasn't been removed.

[tdi90]

In that case drop them an email and tell them its faulty. Probably cost you postage both ways but still cheaper than buying a new MAF.

[mh007]

It definitely sounds like your MAF is faulty.

I wouldn't imagine you'd have much of a problem with warranty even though you've damaged the sticker a little.

It does make you wonder wether these units are actually genuine Bosch units ? !

Do as tdi90 has suggested & drop them an email with all your purchase details & the problem you are having.

Personally, I would flatly refuse to pay any postage & insist on the faulty unit being collected if the seller cannot provide some sort of postage paid label for you to print.

As it falls under warranty, it is the sellers responsibility to arrange collection (if you request it) & provide a replacement if proved to be faulty.

Take plenty of pictures before sending & wrap it really well !

[tdi90]

I dont doubt they are geniune. The op's and mine are the only ones I've heard of that have gone out of spec from that seller. Loads of others from the forum have the MAF from the German seller without issue (including the 1 that I got for a mate at the same time as mine).

There will always be the odd few from a batch that go wrong just like everything else.

[CMWI]

Is it this one? http://www.ebay.co.uk/itm/Land-Rover-MHK101130-75-ZT-MG-Mass-Air-Flow-Sensor-Meter-BOSCH-0928400520-MAF-/131232569544
I bought one back in May last year to replace a Pierburg/MAFAM set-up.
It was fine for a few months but then I had a flat spot between 1500 and 2000 revs, resetting error codes on T4 solved the problem but now it is back again :shrug:

[r44flyer]

Yes, that's the one. I do believe they are genuine, and whilst I cannot remove it from the housing it appears identical to the factory supplied Bosch maf that I still have in the shed.

Same flat spot as you, CMWI. It wasn't there when I installed it, but it hasn't taken long :( In fact, it was silky smooth when first fitted.

I have sent them a message so we'll see how it goes.

[CMWI]

Only happens when the car is warm and on a really hot day like today it is worse still.
See what they say and then I'll go from there, cheers.

[r44flyer]

I have had a reply from the seller. They want me to return the maf but with a 'diagnosis report' from a garage as some kind of proof that the maf is faulty. Exactly what data they are expecting from the garage I know not, but I have asked. Unplugging the maf and observing the obvious change in performance myself is not good enough.

If I do not provide a garage report they will send it to their supplier for testing (presumably on a bench) and if it tests ok I will be billed for the tests (unknown amount) and the maf returned to me. If faulty, a replacement will be sent.

I'm not sure how they test a maf on a bench or whether they will be able to replicate its operation when fitted to the car. I don't know what data they would be looking for or whether it's possible to test the maf as within spec when it still gives symptoms of poor performance when fitted.

Seems like it's deliberately difficult to get a clean refund or replacement and the thought of additional cost could leave me deeper in the hole with no working maf at the end.

Is it guaranteed to test as failed?!

[Avulon]

You really need a read of the MAF performance from a T4 to positively confirm the faulty MAF I suspect.

[HarryM1BYT]

I have had a reply from the seller. They want me to return the maf but with a 'diagnosis report' from a garage as some kind of proof that the maf is faulty. Exactly what data they are expecting from the garage I know not, but I have asked. Unplugging the maf and observing the obvious change in performance myself is not good enough.

If I do not provide a garage report they will send it to their supplier for testing (presumably on a bench) and if it tests ok I will be billed for the tests (unknown amount) and the maf returned to me. If faulty, a replacement will be sent.

I'm not sure how they test a maf on a bench or whether they will be able to replicate its operation when fitted to the car. I don't know what data they would be looking for or whether it's possible to test the maf as within spec when it still gives symptoms of poor performance when fitted.

Seems like it's deliberately difficult to get a clean refund or replacement and the thought of additional cost could leave me deeper in the hole with no working maf at the end.

Is it guaranteed to test as failed?!

Its a MAF, it just measures the speed and thus the volume of the air flowing past it and outputs a voltage to represent that flow.

If I wanted to set up a test rig, I would need a a flow of air at various calibrated speeds and then be able to check the voltage against a graph.

Even a T4 cannot do that, it relies upon the airflow itself being at spec. at certain engine revs, but that relies upon the EGR being within spec and the air filter too.

I've had mine on both a T4 and checked the reading with my OBD unit and been told by a T4 guy that the usual MAF fault is that the reading goes high and mine is reading high. No one has been able to tell me what the reading actually ought to be at what revs, but my car drives brilliantly with and without the MAF.

In your position, I would be inclined to find someone with whom you could do a temporary MAF swap with.

I agree the company is being more than a little awkward with you, in their attempts to avoid your claim. Maybe point them to this thread and explain this is not good publicity for their company?

[MSS]

I have had a reply from the seller. They want me to return the maf but with a 'diagnosis report' from a garage as some kind of proof that the maf is faulty. Exactly what data they are expecting from the garage I know not, but I have asked. Unplugging the maf and observing the obvious change in performance myself is not good enough.

If I do not provide a garage report they will send it to their supplier for testing (presumably on a bench) and if it tests ok I will be billed for the tests (unknown amount) and the maf returned to me. If faulty, a replacement will be sent.

I'm not sure how they test a maf on a bench or whether they will be able to replicate its operation when fitted to the car. I don't know what data they would be looking for or whether it's possible to test the maf as within spec when it still gives symptoms of poor performance when fitted.

Seems like it's deliberately difficult to get a clean refund or replacement and the thought of additional cost could leave me deeper in the hole with no working maf at the end.

Is it guaranteed to test as failed?!

It's worth looking at this from the supplier's viewpoint. If they replaced MAF's whenever a purchaser claimed that it was faulty, I suspect that the cost of the MAF's on average would be 50% higher than it now is.

Whilst this is not commenting directly about you or your situation, I feel that their approach is consistent with the norm and not unreasonable. Those who have sold items on well known auction sites will no doubt have experiences of dealing with people whose behaviour unfortunately leads to the norm being what it is.

The warranty is to cover manufacturing defects and premature failures so it is not unreasonable that the requirement is on the one who is claiming the item to be faulty to provide some evidence to support the claim.

A T4 provides a strong indication of operation within specification and if you are certain that the MAF is faulty, you should confirm with the supplier that they will accept the readings from a T4 on the testing garage's official paper. Also, you could try asking that if the results are conclusive in your favour then they refund the cost of the test as well as replacing the MAF.

To me, their terms for dealing with the situation seem totally reasonable. What else can they realistcally do?

If I was in your situation and did wish to prove that the current MAF is faulty, I would buy a new one and have both tested on the car one after the other on a T4. Then, based on the results, decide whether it's worth pursuing the supplier to get your money back for the first one.

[HarryM1BYT]

To me, their terms for dealing with the situation seem totally reasonable. What else can they realistcally do?

If I was in your situation and did wish to prove that the current MAF is faulty, I would buy a new one and have both tested on the car one after the other on a T4. Then, based on the results, decide whether it's worth pursuing the supplier to get your money back for the first one.

If the supplier really has a testing facility in place, it will not cost them much to verify the operation is within spec or not, its called customer service, but it seems a good option to ask them if data from a T4 would satisfy them. Personally, I would doubt they have any test facility in place at all, other than Bosch having such.

I would not advise laying good money out on a second one from them, as you may then have to fight for a refund. If a known good borrowed one fixes the issue, then it must be at fault - is there no one you could borrow one for, for a half hour test?

Another way would be to tap a voltmeter into the output wire and have someone log the voltage at various engine speeds for you, then post the results on here.

[r44flyer]

I don't disagree with any of that, mss. The point is there's no clear definition of what constitutes a failure. I would certainly expect to be reimbursed for any testing that proved the maf to be faulty.

I will try a multimeter reading as FrenchMike has posted on before, prior to arranging a T4, and see if it's obvious.

Thanks for your input, Harry. There's no way they would be able to replicate anything other than an idle voltage I guess, so that's the only figure that will prove a fault.

Watch this space.

[r44flyer]

Harry, you've used an Autel to read maf values in the past haven't you? What model was it, and does it give you voltages or air mass values? I have an MS309 somewhere I could dig out.

[MSS]

If the supplier really has a testing facility in place, it will not cost them much to verify the operation is within spec or not, its called customer service, but it seems a good option to ask them if data from a T4 would satisfy them. Personally, I would doubt they have any test facility in place at all, other than Bosch having such.


The way I read it was that the supplier will send it to their supplier for testing. The supplier's supplier probably being the manufacturer.

Unfortunately, old fashioned customer service based on trust no longer exists in most situations. Human greed and misbehaviour has killed it:}

[Kenton]

It's worth looking at this from the supplier's viewpoint. If they replaced MAF's whenever a purchaser claimed that it was faulty, I suspect that the cost of the MAF's on average would be 50% higher than it now is.

Whilst this is not commenting directly about you or your situation, I feel that their approach is consistent with the norm and not unreasonable. Those who have sold items on well known auction sites will no doubt have experiences of dealing with people whose behaviour unfortunately leads to the norm being what it is.

The warranty is to cover manufacturing defects and premature failures so it is not unreasonable that the requirement is on the one who is claiming the item to be faulty to provide some evidence to support the claim.

A T4 provides a strong indication of operation within specification and if you are certain that the MAF is faulty, you should confirm with the supplier that they will accept the readings from a T4 on the testing garage's official paper. Also, you could try asking that if the results are conclusive in your favour then they refund the cost of the test as well as replacing the MAF.

To me, their terms for dealing with the situation seem totally reasonable. What else can they realistcally do?

If I was in your situation and did wish to prove that the current MAF is faulty, I would buy a new one and have both tested on the car one after the other on a T4. Then, based on the results, decide whether it's worth pursuing the supplier to get your money back for the first one.

My T4 measures the voltage all the way through the rev band, upp to about 3VDC if i remenber, and then all the way down again as revs decrease?? :smilie_re::shrug::shrug:

[MSS]

My T4 measures the voltage all the way through the rev band, upp to about 3VDC if i remenber, and then all the way down again as revs decrease?? :smilie_re::shrug::shrug:

I thought that's the sort of thing it was supposed to do.;)

[r44flyer]

I thought that's the sort of thing it was supposed to do.;)

I didn't. I thought it went out of spec when revs increase under load.

[r44flyer]

The way I read it was that the supplier will send it to their supplier for testing. The supplier's supplier probably being the manufacturer.

Unfortunately, old fashioned customer service based on trust no longer exists in most situations. Human greed and misbehaviour has killed it:}

Yes, this. I return it, they send it to their supplier, whomever that is. I have to trust that whatever test procedure is in place is actually carried out and is relevant. If it turns out to be 'within spec' I'm held to ransom for my faulty maf. I do accept that carrying the cost of testing perfectly good mafs wouldn't be good business, but I shouldn't have to shoulder the cost either, and by reversing the element of trust the risk for the customer is increased so as to scare them off. Consumer law exists to prevent this kind of thing.

It is a shame it is this way around, I have no interest in trying to rip them off, but they're being too vague so far.

[CMWI]

Maybe this has always been the case and one of the reasons (apart from the cost) why the Pierburg MAF and RoverRon boxes became popular?
I swapped a Pierburg and a MAFAM that was on my car for a 'Genuine' Bosch in order to return it to the original spec and now wish I had left it alone.
Just returned from a 100 mile round trip with the MAF unplugged and the car pulls like a train with no flat spot or any 'fluffing' or hesitation at all at low revs :shrug:

[MSS]

I didn't. I thought it went out of spec when revs increase under load.

I was merely commenting that the voltage is supposed to increase with revs. This based on French Mike's reference readings - I have never actually done the test myself.

When Terry at tsauto was testing mine, I got distracted by a phone call so didn't actually note which way the voltages went.

[r44flyer]

This I may end up doing, especially if I have no joy on a replacement or refund. I can't afford another maf. There are a few good reports by some members who have clocked up decent mileage now with no maf connected and no obvious down side, eg. economy.

I did intend to get the 160 remap done, though. This may change things as I don't know how sensitive this is to their being a maf at all never mind an out of spec one. I have already had a synergy with pierburg maf, and I want to try the remap.

[r44flyer]

I was merely commenting that the voltage is supposed to increase with revs. This based on French Mike's reference readings - I have never actually done the test myself.

When Terry at tsauto was testing mine, I got distracted by a phone call so didn't actually note which way the voltages went.

Cool, no worries. Terry is my nearest T4 as well.

[HarryM1BYT]

Harry, you've used an Autel to read maf values in the past haven't you? What model was it, and does it give you voltages or air mass values? I have an MS309 somewhere I could dig out.

I'm away from home ATM, so I cannot find out which model of Autel, but any unit should show the same values. I posted my readings at the time, to try to get a reply on whether it was right or wrong, but didn't get any usefull replies - maybe due to the T4 MAF reading glitch, or it being voltage, instead of LPM of air?

On the T4 a few weeks ago, I was told the idle reading was OK but the 3000RPM test showed to high a value and that that was the usual failure mode of the MAF. So I would suggest it would be pointless them checking it just at idle airflow speed. There is a glitch which is normal in the T4's reading where it does not give a continuous reading throughout the rev range - perhaps BigRuss or one of the other T4 guys could comment more on this?

My Autel gave continuous readings through out the range. The Autel I have can produce a graph of rpm versus MAF output, which is handy ;)

I wish I could find my original post on my MAF readings with the Autel, but I could not.

[HarryM1BYT]

This I may end up doing, especially if I have no joy on a replacement or refund. I can't afford another maf. There are a few good reports by some members who have clocked up decent mileage now with no maf connected and no obvious down side, eg. economy.

I did intend to get the 160 remap done, though. This may change things as I don't know how sensitive this is to their being a maf at all never mind an out of spec one. I have already had a synergy with pierburg maf, and I want to try the remap.

I understand you only get full value out of the 160 if the MAF is working fully, I was also told that with no MAF mpg drops by 4% anyway.

Mine feels fine, despite its high reading MAF and consumption is pretty good. I this past 7 days in holiday mode, reproduced my earlier 64mpg on the dash over a fair mileage - the entire 7 miles from here to Great Ayton for pies and without holding anyone up :D

[DMGRS]

Threads like these make me glad I try my best to look after customers - expecting a full garage report for a faulty product is nonsense.
I had a faulty MAF back from a member on here - he had the choice of a replacement the next day or a refund, and that was that.
Anything else is contrary to common sense IMO.

[MSS]

Threads like these make me glad I try my best to look after customers - expecting a full garage report for a faulty product is nonsense.
I had a faulty MAF back from a member on here - he had the choice of a replacement the next day or a refund, and that was that.
Anything else is contrary to common sense IMO.

With respect, what you are doing is starting up a business and using every opportunity to highlight how good your service is. Without your excellent service, you may not be competitive on many parts. So, the service is your differentiator or value add.

Until that particular supplier of MAF's was discovered, people were paying at least 50% higher price for the genuine BOSCH item. Your price now is 30% higher than theirs. It is relatively easy for supplier B to offer better service when his/her profit margin on an item is probably 300% that of supplier A.

In short, there are many variables that contribute to "customer service", one of which is offering items at an affordable price.

But let's test something. You know the strutt top bearing set that I brought from you, I feel that the bearings are not working quite right. The car doesn't feel right when turning. I believe the bearings are faulty. Could you send me a replacement set please or give me a full refund?

And thank you in advance for your excellent customer service.:}

My apolgies to the OP for this slight digression.

[Avulon]

The way I read it was that the supplier will send it to their supplier for testing. The supplier's supplier probably being the manufacturer.

Unfortunately, old fashioned customer service based on trust no longer exists in most situations. Human greed and misbehaviour has killed it:}

And if my experience working for a wholesaler (in my case computer parts) is anything to go by then they want to be damn sure the part is at fault before sending it to the the manufacturer or their supplier as they will get charged for the supplier testing it themselves if it's not faulty, and that won't be cheap. So they try to transfer the onus of proof as much as possible onto the , the retail customer who is least well equipped to test it. It would be better for them to say they'll accept the return with a payment and refund the payment (and original purchase price/ or send a new item) when they have found it to be faulty. Of course, you are in a much stronger position if you have it tested yourself; as long as they agree to paying the cost when your tester has proven it faulty.

Its a minefield isn't it?

[Union Wheels]

Hi r44flyer,

I am coming to the meeting at the "Four Ashes" on Saturday, and I have a spare MAF which I can bring. We could fit this and if works OK this would be further proof that your MAF is faulty and add weight to your argument with the supplier.

Cheers, Pete.

[r44flyer]

I appreciate that, Pete, thanks. Unfortunately I'm working on Saturday. Besides, with no 'printed diagnostic report' I doubt they will be interested.

Further, last night I put a multimeter across the maf and unless I'm doing it wrong I got no voltage reading at all. I think I need a printable T4 to prove zero voltage on paper.

[HarryM1BYT]

I appreciate that, Pete, thanks. Unfortunately I'm working on Saturday. Besides, with no 'printed diagnostic report' I doubt they will be interested.

Further, last night I put a multimeter across the maf and unless I'm doing it wrong I got no voltage reading at all. I think I need a printable T4 to prove zero voltage on paper.

If you have the data lead for the 309, you could store the data graph in that, then upload that plus rpm to the PC, print that and forward that at no cost.

I'm on a dodgy Three mobile connection, so I cannot access exact data, but...

At the MAF, there are three wires - positive, ground and signal. Ground will likely be black. So you should see a stable voltage on one (5v I think) and the varying MAF signal on the other. The best way to tap into the wires is with a sharp needle, straight through the insulation.

[r44flyer]

Not sure what this 309 is you speak of Harry.

I have done the needle through the wires trick, that and pushing them through the top of the plug down the side of the wire into the pin, across pin 3 earth (black) and pin 5 maf signal (yellow). No reading at all. Tested on battery and got 14. Maybe I need to try again with more positive connections.

[HarryM1BYT]

Not sure what this 309 is you speak of Harry.

I have done the needle through the wires trick, that and pushing them through the top of the plug down the side of the wire into the pin, across pin 3 earth (black) and pin 5 maf signal (yellow). No reading at all. Tested on battery and got 14. Maybe I need to try again with more positive connections.

I thought you said you had an Autel 309?

[r44flyer]

Omg... doh! Yes I do. Sorry I was having a brain ****. However, I don't have a data cable, just the connection cable.

[HarryM1BYT]

Omg... doh! Yes I do. Sorry I was having a brain ****. However, I don't have a data cable, just the connection cable.

Well you cannot print out the evidence, but at least you can watch the readings coming from the MAF..

[DMGRS]

Take a picture or video of the readings, and include that in correspondence with them. :)

[r44flyer]

My MS309 doesn't give me any readings of any use. It seems to be a fault code reader only, which is maybe why I bought it, so either there's a compatibility issue or it's very limited in its capability. :(

[HarryM1BYT]

My MS309 doesn't give me any readings of any use. It seems to be a fault code reader only, which is maybe why I bought it, so either there's a compatibility issue or it's very limited in its capability. :(

I've just checked, and mine is in fact an MS509, sorry. It shows live readings, can show the data as a graph and can store the graphs data for upload to a PC.