MAFing about!

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The Gas Man 2
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MAFing about!

Post by The Gas Man 2 »

My continuing MAF saga is dragging-on. C4GP 2008 1.6HDI

New MAF fitted to cure intermittent flat-spot. Same problem.
Another MAF fitted (secondhand good quality). Same problem.

But....if un-plug the MAF the car drives superbly (apart from the various warning lights and messages. Really fed-up!

When I plug the MAF back in, after a while the flat spot returns.

I know you shouldn't drive for too long with the MAF disconnected and this may sound bizarre, but is there a MAF wire I could 'tap into' and have a remote switch in the car to turn it off when the problem arrises? If so which wire would I tap into and could I turn the MAFF off/on whilst driving?

Flustrated of France!

Peter.N.
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Re: MAFing about!

Post by Peter.N. »

There are several, two air flow sensors and a thermistor. You could disconnect the earth wire but you might get false information via the other leads, so really you need to switch all three.

Desperate measures but I know how you feel, I have a Merc with a turbo boost fault and have tried disconnecting everything - well no quite it seems!

In my experience MAF's are only effective below about 2000 rpm, that is you can only feel the difference at around that speed.

Peter

The Gas Man 2
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Re: MAFing about!

Post by The Gas Man 2 »

Thanks Peter.

Do you think running with the MAF disconnected will do harm?

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GiveMeABreak
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Re: MAFing about!

Post by GiveMeABreak »

Yes!

The engine ECU relies on the information from the MAF to determine the correct fuel to air ratio. Disconnecting the MAF will result in either too much air air (lean running) or too little air (rich running). Neither of these are good for the engine and can cause rough idling / stalling and smoking issues. So don't leave it for too long. It would seem your MAF is faulty - was it a good quality one? You may be just importing the problem with a second hand one and cheap aftermarket new ones can be of extremely low quality / duff.

Never connect or disconnect the MAF with the engine running. Putting a new MAF on may take a little while for the Engine ECU to adjust to the new air flow readings. A drive about will give it time - but after replacing with quality MAF, a BSI reset may clear some of the old readings. Aftermarket MAFs are known to be junk. But get it diagnosed first as a new decent MAF is not cheap for the reason that they are a quality component.

Peter.N.
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Re: MAFing about!

Post by Peter.N. »

On a lot of my 406's I have not known whether its working or not, the difference is minimal. But they use the 8 valve engine of course.

Peter

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GiveMeABreak
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Re: MAFing about!

Post by GiveMeABreak »

The MAF is certainly needed. After a while it will start affecting fuelling and that can damage your engine components for sure. If it wasn’t needed it wouldn’t be there, but temporarily disconnecting it can be used to identify a faulty MAF on the short term, it don’t leave it.

The Gas Man 2
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Re: MAFing about!

Post by The Gas Man 2 »

Thank you all for your sound advice, I shall get the ECU read and probably have to bite the bullet and buy a Pierburg or Bosch.

I'll report back.

Regards

Paul

RichardW
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Re: MAFing about!

Post by RichardW »

Check what the EGR valve is doing in live data - if it is not tracking the requested position closely, then the air flow can be all over the place, and this causes the sorts of symptoms you are seeing. And it doesn't always set a fault code, or put on the EML!! It can however disable the handbrake, with no real clue as to why it is doing it....

The Gas Man 2
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Re: MAFing about!

Post by The Gas Man 2 »

Do I not need a diagnostic reader to see what's going on? But I have checked the points and adjusted the tappets! :shock:

RichardW
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Re: MAFing about!

Post by RichardW »

Yes - but it's as much an essential tool these days as a set of feeler gauges and a timing light was in the days of points operated dizzies!!

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EDC5
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Re: MAFing about!

Post by EDC5 »

With the MAF disconnected doesn’t the ECU stop EGR operation too?

So the MAF might be the innocent party in this issue and the real culprit could be the EGR.

The Gas Man 2
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Re: MAFing about!

Post by The Gas Man 2 »

RichardW wrote:
22 Apr 2019, 12:48
Yes - but it's as much an essential tool these days as a set of feeler gauges and a timing light was in the days of points operated dizzies!!


Could you point me in the direction of a type to buy, I take it it's the OBD reader type.

Thank you for your help.

Hell Razor5543
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Re: MAFing about!

Post by Hell Razor5543 »

You will need to buy a proper Lexia clone. Generic code readers do not 'read' the PSA vehicles well. You will also need a laptop computer running a 32bit version of Windows (as parts of the Lexia software are so old they use 16bit code that a 64bit O/S cannot manage unless running one a decent 'Virtual Machine' setup). Be aware that there are some Lexia clones on ebay that do not have the full chipset, and so cannot communicate with some of the modern PSA vehicles.

Easy Diagnostics do a good, full chipset Lexia clone. It is not cheap, but they know what they are doing, provide proper aftercare support, and a one year warranty. There is also (through this forum) a discount available to Forum members. Here is that process;

viewtopic.php?f=13&t=60113

I have an earlier Easy Diagnostics Lexia system, and I feel it was well worth the expense. If I ever have to replace it I will almost certainly go back to them.