Diesel Cats, can they become clogged?

My HDI 90 (actually in a Xsara) doesn't want to rev over 4000, and the fuel
consumption is rather worse than I had expected. It pulles really well at
lower revs, far better than the 1.9 TD in my old 405.
It was serviced, according to the manual, 3000 miles ago by a main agent, so
I assume that all the filters are OK, certainly the air filter is as I have
checked. It has done 40,000 miles.
I know from previous experience with marine engines that a clogged exhaust
on a diesel can give this symptom, but I can find no reference to any
maintenance on the cat, though the early information from PSA on the HDI
engine said that they had a special fluid which was injected into the cat at
certain intervals to burn off the particles trapped there.
Can anyone enlighten me please?
Brian.

 

Hi Brian.
Can't help with the query, I'm wondering about that diesel cat myself.
Word on the street is... You can take it out, or more specificaly buy a
straight through pipe without compromising the UK MOT.
I would have thought getting to it to inject anything would be tricky to say
the least.
The only problem I've encountered was a holed pipe directly in
front of the cat, which looked like a possible blocked cat causing back
pressure.
Fitting a new one didn't give any noticable performance increase though.
Erm...... 4000RPM? Doesn't that equate to over 105MPH in top?
All the diesels I've owned ran out of steam around 4K RPM
I've never felt the urge to push mine (HDi90) past 3K in the gears
there doesn't seem to be anything to gain.by it.
Is it possible that your pump governer has been set at 4K RPM?
ie. will it rev past there in neutral?
The fuel consumption on this 406 HDi is much better than my old 406TD
though, (It's about 50mpg the same as my old 405 normaly aspirated diesel)
so you may have a problem somewhere, If it is actualy worse than your 405.


jim.

 

as a rule if it has this system and becomes blocked it will tell you on the
inst panel because it incorporates up and downstream pressure sensors
so i suspect that yours is just a cat and yes they can get blocked

 

Can anything be done if the cat is blocked? I suspect that the car has just
done the shop run daily which does cause crud to build up in any exhaust,
but the cat would not self clean so easily.

 

to be fair you need to establish that this the problem and not some other
fault

 

if its just the exhaust a run to the limiter through the gears would soon
clear it out!! (aka Italian tune up)

(only once up to temp though)

HTH

Lost

 

Bit difficult when it won't rev over 4000 on load.

 

What other fault could it be, I'm open to all suggestions.

 

bit of a noisy option but you could try it with the front pipe disconnected

 

also check air filter fuel filter etc

 

also how high is the milage
did the main agent fit a timing belt ,has the belt been mistimed/??

 

It has now done 40,000 and there has been no change of timing belt AFAIK.
Last service was at 36k by main agent. Air filter definitely new, have not
checked the fuel filter yet. Pollen filter should also have been changed,
and the one in there looked as if it was as old as the car! No wonder the
ventilation didn't work.
Not sure about running it without the down pipe connected, ran out of ear
plugs yesterday.

 

i know its noisy but i have done it
having said that i'm a maniac