Car says catalyser is blocked

It is possible to read it but very frustrtaing to do so. It requires a mouseclick and hold the button down so you can scroll about in the limited window to move the document for reading. The trouble is that you have to release the mouse to move lower down the page and the viewing window may well close on you, fail to repeat respond etc. I managed about a page and a half before I gave up the battle.

pgk

In the DailyTelegraph Motoring Supplement, Honest John recommended, driving for 20 - 30 miles to warm the engine and then driving at 5,000 rpm for several miles (Presumably Petrol, where a diesel would need to be at 4,000 rpm probably )

The engine needs to be running on as great a load as possible, to maximise exhaust temperature, to light off the catalyst and to burn off burn off excess carbon.. So high revs and high load, not low gears.

Clive, a third or fourth gear, full throttle blast up Wrotham Hill on M20, perhaps?

The Mazda 6 diesel used to upfuel, if the DPF did not regenerate automatically.

If still driven gently, the excess fuel could drain down into the sump.

I was told that the Instruction book stated if the the oil level reached an "X" mark, above MAX on the dipstick, the vehicle was to be taken immediately to a dealer for an oil change.

There were instances of engines running away on the diluted oil ingested from the closed circuit breather.

Often the damage is terminal for the engine, with pistons and injector tips melted!

If you have not witnessed a diesel engine running away, you have not missed anything. The acceleration is tremendous, and switching off has no effect. The engine is totally out of control.

I saw it on a test bed, (Deliberately ) and was able to disconnect the breather pipe. In a vehicle you can't. Declutching will overspeed and destroy the engine, and the brakes are going to struggle to contain things.

On the subject of Commer TS3; drivers used to Leylands or Gardners, which would lug down to idle speed, did not get on well with the TS3.

On Southdown, as a result of using cheap straight oil, on the Brighton to London express services, crankcase explosions forced a change to Shell Rotella.. Slogging the engine caused the wet liners to shift, allowing coolant into the sump. I saw engine changes at as little 35K miles, never more than 65K.

They were best kept above 1600 rpm. But being high geared, much over 2,000 was rarely available. Once I saw 2300 in fifth going down Peaspottage hill, on the A23. The speedo read 6:30 on the tiny watch that did duty as a clock, well past the final 70 mph graduation. The only thing to pass was a Lotus Cortina!

On TS3 powered tractor units the exhaust silencers were mounted across the front, beneath the bumper. On a Friday night, after a week around London, on the M1, there were often quite spectacular firework displays. On one occasion, I saw the tailpipe melting, with the final silencer red hot!

Howard

I've got a Peugeot 3008 with a 1.6 HDI diesel and about 18 months ago had a warning come up that the DPF needed attention. the mileage was ~ 125,000 mostly fast dual carriage way and motorway.

Did the requisite 60 miles up and down the motorway a noisy affair in low gear. Still no joy ,message still there.

My diagnostic unit could find no error codes or anything to reset.

I took the DPF core out ,washed it with hot water and Fairy liquid. Black soot followed by pink sludge, possibly the residue of the Eolys DPF additive , followed by a good high pressure hose rinse. [ I avoided the pressure washer as I didn't want to damage the ceramic core] . Finally a vac out of the core with a Wet & Dry vacuum cleaner. Then overnight drying in the Rayburn .

The Message adamantly refused to go away. I did read in a Forum that if the message were ignored the car could go into "Limp Mode" , having had that on an Audi [many times and ££ to sort] it was time for a professional.

Reluctantly I took it to a specialist who plugged in their diagnostic unit ....checked out the temperatures and differential pressures ,all were well within spec, and no errors logged. He finally told the on board computer that the DPF had been replaced. Joy ..... message gone no more problems and trouble free driving for 10,000 miles since

From what I understand, ......the on board computer is set for the DPF to need attention when the differential pressure across the core exceeds set limits , in addition it will display a message due to "potential blockage" by residues [ DPF Additive ?] regardless of the actual differential pressures across the core,  at around 120,000 miles.

If anyone knows an alternative real reason I'm ready to learn !

Edited By The Novice Engineer on 21/10/2020 16:49:55

From what I understand, ...the theory goes....the on board computer is set for the DPF to need attention due to "potential blockage" by the additive residue regardless of the actual differential pressures across the core at around 120,000 miles.

If anyone knows an alternative real reason I'm ready to learn !

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I was told by the Subaru Dealership that if left without doing anything it would end up wrecking the Turbo, my car also doesnt use additive.

Martin P

Edited By martin perman on 21/10/2020 16:59:17

Edited By martin perman on 21/10/2020 17:00:24

I'm not suggesting anyone tries this, could be expensive if it went wrong, but the routine for decoking carbonised vapourisers in paraffin blowlamps was to take it off, get it red hot with an oxy torch, then turn off the acetylene and direct the oxygen down the inside of the pipe. The burning carbon kept it all hot, and moving the tip of the oxygen torch in and out gave some measure of control. I can't help feeling some enterprising chap could come up with something similar to clear DPFs, in a rather more controlled manner of course

Friend of mine years ago had a petrol Audi with a cat fitted when the law didn't require one. It developed a strange fault when it would suddenly lose power, but then equally mysteriously clear itself. Turned out the core of the cat had come lose and by moving about inside the outer casing it had gradually gone barrel shaped. It could then roll to one end and block the exhaust. Cure was either a new cat, very expensive, or cut the outer case, pour out the matrix, weld the case back together and carry on. As he is no longer with us I can reveal that he took the cheaper option.

Hi Clive, apologies for not seeing this post before.

If I may suggest, the way to clean a DPF is high temeperature in the exhaust system and a higher than normal gas flow.

40mph in your car in top gear is not nearly pulling enough revs to adequately provide the oxygen required to burn off the DPF.

During a regeneration, which will only start when the exhaust temperature reaches a set point, the ECU will inject additional fuel into the exhaust along with any regeneration fluid (some vehicles have seperate tanks for this) normally an eolys fluid which will combine with the fuel and additional oxygen in order to raise the exhaust temperature still further and effectively regenerate the DPF.

So, in essence you need revs, temperature and distance, revs should be 2000 - 2500 (40mph in top willl be well below this) , temperature - runnng at fully warmed up on the temperature gauge will normally be enough, and distance - 30 - 40 miles.

Go out for a decent drive and get theengine up to temperature, if possible get on a motorway or fast A road, select a gear that allows the required rev range without intimidating plod, and keep it there.

I normally do around 60 mph in third for the requred distance.and my old peugeot van (146000Miles) needs this every month or so.

Hope this helps, and goodluck.

Don't forget, diesels with DPF's also have a cat, so the op may well have a different problem to most of the answers. I have a 7 year old 1.7 Corsa and have had no trouble with the DPF. The car does get a long drive every other tankful to make up for the short hops it has too many of. The trouble is that with my car, an Italian tune up would be unwise as the car can go 124 mph.

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Might one be correct in assuming that it has a range of gear ratios available ?

... The idea is surely to thrash the engine, not the drive-train.

MichaelG

The trouble with revving the engine in a low gear is that only a tiny amount of throttle is needed.

Lower gears don't really do it if the DPF system is well clogged. Need to get the motor under decent load and decent revs simultaneously to clear it.

Light footed drivers like me can get the DPF system into trouble even with a theoretically appropriate mix of fast motorway runs. I long ago mastered the art of getting cars with SU carbs settled nicely at motorway / open road cruising speeds with the throttle backed right off. Still applicable to moderating the thirsty Rover / Buick V8 in my P38 Range Rover!

Clive

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I do realise that it’s a balance, Clive ... but a lower gear and a steeper hill should do the job nicely without risking a speeding conviction !

Note: I don’t drive a diesel engined vehicle, so the intricacies are unknown to me.

MichaelG.

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Hence my choice of words ... ‘thrash the engine’

... Hopefully my response to Clive adds clarity.

MichaelG.

What I have is an M2 trip down to the West and over the Medway bridge turn around and then drive back up the hill to my turn off.

I power up the hill and can reach a good speed so that should do the trick.

Clive

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Sounds like a good plan, Clive

“Don’t spare the horses”

MichaelG.

The key point is to get the exhaust and DPF hot enough. This requires a load on the engine. The load is the same for the same road speed and incline / load / wind regardless of engine speed. However higher engine speeds mean more combustions per minute and higher exhaust flow so generally higher exhaus temperatures. And of course if you do it for the same time you will have done more miles.
It's bad to generalise though as different engines have different systems.Some have an additive (which may be hidden from the driver). Others don't need this but my hve to regenerate by injecting extra fuel either directly into the exhaust with a valve or by opening the injectors on the exhaust stroke. How often this happens depends on driving condtions and style and alo fuel quality.

Robert G8RPI.

There is no actual 'Throttle' on a diesel engine unlike its petrol counterpart.

The amount of air drawn through the combustion system is directly related to the rpm of the engine, not how hard you tread on the loud pedal.

As I referred earlier, a full active DPF clean needs temperature, gas flow and the addition of a fuel bourne catalyst (adblue, or a more potent - and highly nasty to handle chemical like Eolys).

It doesn't really matter what 'speed' you are doing as long as the pumping action of the engine is high.

Many older cars have non-active DPFs which do not need a fuel bourne catalyst additive - when they block the only recourse is to visit one of these specialist DPF / Catalyser cleaning firms that are popping up nowadays, or replacing the whole unit.

Fun this, isn't it?

I think it is accepted that a Diesel engine does not have a throttle valve in the traditional sense, what was referred to here was a 'tiny amount of throttle' AKA only gently depressing the throttle pedal. However, some Diesel engines do have an ECU controlled throttle valve in the intake tract to increase manifold vacuum and increase EGR flow, and it also closes at engine shut-down to reduce engine shudder as it comes to a stop.

AdBlue is for SCR (selective catalytic reduction) of NOx within the exhaust gas - it is not involved in DPF regeneration.

fuel bourne catalyst (adblue,

Adblue is not "fuel borne" & is nothing to do with cleaning a particulate filter.

Add Adblue to your fuel & you will end up coming to a very expensive stop !

Nigel B.

Theft is not due to the associated problems, its because they contain a considerable amount of precious metals, mainly platinum I believe, thus worth a lot as scrap and the problem is not confined to Essex !

John

Apologies on the reference to Adblue, I ony have cars with either a seperate FBC tank or none, and incorrectly assumed that the Adblue additive had the same purpose.

Sorry.