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Excessive regen - MAF wiring?


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Hi all,

Over past year I have been trying to hunt and issue on my 2011 Mondeo, 2.2TDCI (200ps) 6 speed manual.

It all started with me noticing poorer fuel economy (getting worse over extended period of time), then frequent regenerations started. During a non stop 270km trip (mostly empty B-roads) it did regen 2 times. Lastly it seems that car is a bit down on power, especially on lower revs.

Ford dealer refuses to look in to it, independent specialists also seem clueless and every diagnosis is different. Had my DPF removed to take  look and clean it - everything was fine, not plugged and no ash deposits. DPF pressure sensor seems to read fine, all hoses are ok. DPF diesel evaporator is not clogged and looks fine, overall I would say - regens are performing normally, but for some reason DPF gets full quickly.


The only odd thing I have notices so far in Forscan is - my MAF sensor reading with the engine turned off is more than 3g/s. I replaced it with the same MAF from other car (Ford Focus) to test - on my Mondeo both sensors are showing 3g/s with engine off. On Focus both sensors are showing zero.

If somebody has the same car and engine and could tell me their MAF reading with engine off, I would really appreciate it!  Would like to rule out wiring issue before taking out injectors.


Thanks and hope you have a nice day!

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This is my 2011 2.2 TXS with the engine off.


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2 hours ago, Frembrit said:

This is my 2011 2.2 TXS with the engine off.


Thank you very much Frembrit!


Seems like the ~3g/s MAF reading with engine off is just a quirk of the ECU.


Guess I'll have to start planning the injector replacement 😅

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Injector? do you mean the Vaporiser in the exhaust? If it's doing a regen every time then won't the vaporiser be ok (although it can be partially blocked).

Are you getting any other error codes? does it always regen or does it sometimes fail? Is your car still using the original DPF? I read that the after market DPF's fill up too quickly and cause regens to occur more frequently.

My original vaporiser completely blocked up with carbon and I replaced that in 2017 (I think). Since then it has been generally behaving itself and regens are fine. However since Covid I haven't been driving so much and  I now get the odd failure (open circuit), I just reset the error code and carry on and it eventually regens....my car really doesn't like not being used, though have done about 900+ miles in the last 5 weeks, which helps.

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I meant the main fuel injectors.

Overall I would say that regeneration performes ok. I have been trying to monitor it as much as possible via Forscan. Have seen it stopping more quickly a couple of times (at around 50% soot level), but I think it was due to idling in traffic or cold temperature (winter time). Otherwise it always gets up to the temperature and regens for 15 minutes (rough estimation). 

One thing I have noticed over time is that soot level percentage value right after regen is slowly going up. When car was performing well, it went down to 12%. Nowdays it indicates 29%, this change slowly happened over a 1.5 year period.

My initial thought was that the DPF is getting clogged by ash deposits. To check it, I brought my car to independent shop, which specialises in diagnostics and car performance tuning (supposedly best one in my country). They said that DPF is full of ash, that is the reason for frequent regens and poor fuel economy, only solutions are to replace it with OEM one ( 1500EUR + work), or to take the DPF out. Of course they recommended to remove the DPF, which at very least is illegal, so I started to doubt this specialist.


I decided to take a closer look at things myself. I removed the DPF, checked the hoses and sensors, everything was fine. Then I used a DPF cleaning solution to clean the DPF- only some black soot came out, nowhere near as bad as videos on youtube with blocked filters being cleaned, and absolutely no red (ash) deposits. 

During this I also visually inspected the fuel vaporiser- it did not seem to be clogged, only a bit of carbon on the surface, but the hole was clearly clean.

After all this I reassembled everything and have been driving around for couple of thousand kilometers - no changes in the behaviour.

There are no active fault codes I can see in Forscan, no boost leaks I can find (yet to perform a full pressure test, but a split pipe should be easily noticeable). Cant guarantee the DPF is original, since car was purchased second hand, but during the removal it did not seem to be in different shape than the rest of exhaust.


Car just seems to use more fuel as well as be a bit lazy until higher RPMs and regenerate often. When I originally got the car, it would do around 7l/100km with quite active driving. Now I struggle to get that during a 110km/h cruise during the night without traffic.

One other crazy idea was that the turbo vanes are acting up, but logic dictates that engine sprays fuel according to MAF sensor... Maybe I am wrong tho...

EGR also should not be the reason, as I have fitted a new one.

Engine does not consume any coolant or oil. oil does not seem to be diluted with fuel and is changed every 10k kilometers.

For me it seems that DPF is just being filled up unreasonably quickly, and I currently cant think of any other reason other than the one (or more) of the injectors is faulty and is dumping excess fuel. 

However I am open to other ideas!

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