Have you had any further incidents of this, similar to what you reported at the start of Feb, like a loss of power?
Reason I ask is, just had a "stutter" on my new Mondeo, as if I had dipped the clutch sharply then re-engaged it, while at medium rpm on a dual carriageway, the engine note was also different and a bit more dieselly / "boomier" for a short time afterwards.
It was all fine and as normal on the journey home.
I'm wondering if the ECU ordered a DPF regeneration, and the stutter / new exhaust note was due to the regen happening.
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Not sure... but probably nothing like Feb which was after mostly local driving for a while.
Driving from Manchester to Slough today I thought it might have done it but once might have been me hovering on the clutch due to about to change gear. Also a few times it seemed to be around 2000-2100rpm when I was lifting off the accelerator totally (slowing traffic).... maybe it's a quirk of my Mazda engine???? But it was nowhere near as abrupt as in Feb - it was as you say as if the clutch was dipped.
You reporting back on a Mondeo doing the same (you got the new one?) makes me think it might be DPF after all. Like you I'd say it was like the clutch was dipped abrubtly and let back in. But for a very short time.
When I described all of this to my Mazda dealer they said it sounded like DPF.... and they claim some do not notice! He basically said normal fuelling is stopped during DPF (is it?) to burn off the old soot on the filter. Kind of makes sense. Trying to burn off the particles on the filter with high temperatures so you don't really want more particles. When I was in someone was on the phone to him with allegedly the same symtoms.
My manual does say engine noise and even exhaust smell will change during DPF. Since the issue in Feb I've done over 2000 miles without a problem. I've tried the usual tests of clutch and it seems not to slip - my previous Mondeo did have clutch slip at 47k miles so I know how to test for that now ;-)
But if this is a symptom of DPF regeneration.... then a big bold statement in the manual would alleviate some worries.
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Yes, it's a new MkIV 2.0 TDCi, done about 550 miles of mostly local work. This happened after I'd been driving for 20 mins, was on the dual carriageway at 2500rpm in 5th, at steady but light throttle.
It was quite abrupt but lasted for less than a second, with a slight driveline snatch, as if I had lifted right off the throttle quickly then got back on it again.
There was a definite change in engine note too, it sounded more thrummy, like my Passat PD used to.
The Ford manual mentions the DPF, and how the car should be driven at medium revs for 25 miles every 300 - 500 miles to initiate regen, but doesn't mention changes in engine noise etc. Maybe they assume most drivers won't notice ...
From what I can gather, when the engine and exhaust are hot enough, the ECU will overfuel for a short while to make the exhaust hotter still, and start "cokeing" the soot in the DPF. Once this is started, the soot will burn itself without further overfuelling.
Perhaps the sensation we feel is the overfuelling starting ... perhaps without the "slowdown" we would get unintended acceleration ...?
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craig
That's a very plausible reason, it could well be changing-over fuelling maps.
It doesn't overfuel in the conventional sense - that would just cause more soot; but uses the multi-pulse ability of CR to continuously inject fuel after TDC, [post-injection] which doesn't burn in the engine, but ignites in the hot DPF.
Think of regeneration as a sort of horizontal chimney fire and you'll get the principle.
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Craig
From your description thought you have experienced exactly the saeme symptoms I posted about. It really did feel like someone dipping the clutch and letting in quickly - like one of those Microsoft MES ECU's in F1 ;-)
I know DPF = overfuel somehow and I'd be happier if someone official via Ford/Mazda/etc said you might see this. I cannot see how some do not notice. Except so many are said not to nitice faults full stop.... or should I say "choose" not to notice. Yours and my my experience pretty obvious and different engines.
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I did sort of know the extra diesel goes to the DPF (and not engine) hence the hesitance. But for me it was so sudden and easily sensed I suspected clutch problems. Not that I should care.... lease/company car.
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The OTHER thing I noticed, which I remembered after posting, was that the stutter was accompanied by a clearly audible 'pop' (the engine is very quiet at cruising speeds), it was exactly like a small backfire -- so I'm pretty certain it was the ECU starting a regen cycle.
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Interesting article on the AA site about DPF's
www.theaa.com/motoring_advice/fuels-and-environmen...l
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@rtj -- if you get the chance, would you be able to post the text from your owner's manual about DPF regeneration?
This is what the Ford manual says:
"Unlike a normal filter which requires periodic replacement, the DPF has been designed to regenerate, or clean itself to maintain operating efficiency. The regeneration process
takes place automatically.
"However, some driving conditions mean that you must support the regeneration process. If you drive only short distances or your journeys contain frequent stopping and starting, you must initiate the regeneration process every 500-800 kilometres (300-500 miles).
"To do this, drive your vehicle at 80 km/h (50 mph) for 40 kilometres (25 miles) in the lowest possible gear whenever it is safe to do so. Alternatively, drive normally but use a lower gear."
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Interesting to see the AA recommend a petrol car rather than a diesel with a DPF if your car use is mainly urban stop/start. Progress :-)
Edited by nick on 19/03/2008 at 09:04
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I'm now pretty sure that the ECU orders an 'active' regeneration based on a simple time interval (i.e. number of hours driven), as well as passive regeneration when driving.
This must be a failsafe to clear the DPF if normal driving does not start a 'passive' regen.
In the past week I've done several hundred miles of high-speed, high rpm journeys (including one 40-mile stretch at a constant 2750rpm in 5th) so the DPF **should** be good and clear through passive regeneration.
However, yesterday I was driving my normal 4-mile journey home from work, having started the engine from stone cold.
As I was in the 30 limit in my town (after 3 miles driving), I felt that pause as if I'd backed off the throttle slightly, and the engine note changed to a thrummy, deeper noise. I could also hear the cooling fan cut in (temp gauge was were it always is, just below the middle mark, so the fan did not need to cut in).
This continued as I parked outside my house, so I thought I'd leave the engine idling to see what happened. The fan continued to run for 2 minutes, and I also noticed the end of the exhaust tailpipe was too hot to touch -- which it would NOT be after a normal 4 mile journey from cold.
I turned the engine off when the fan cut out.
I now believe that after a certain number of driving hours, the PCM orders a regen whether it's needed or not ... if there's very little soot in the DPF, it will just burn off quickly. And when an active regen is happening, the fan cuts in to help remove the extra under-bonnet heat from the DPF casing & exhaust.
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CubicCapacity, that is an astonishing report by the AA.
As nick mentions, the AA say: "If your own car use is mainly town-based, stop/start driving it would be wise to choose petrol rather than risk the hassle of incomplete DPF regeneration."
An eye opening thread, guys.
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Mine hasn't done it since - fingers crossed. Now around 8400 miles on the clock.
What I don't understand is why my previous Mondeo 130PS TDCi was able to be Euro IV complaint with lower emissions of CO2 without resorting to DPF? Okay I know the Mazda6 is 143PS but I've heard the Mondeo was closer to around 147PS in the later models.
I can see why DPF might be needed for EuroV and later though.
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