2.0Hdi poor fuel economy black smoke

[bradspau]

Hi all. I have a 2006 Citroen C8 2.0Hdi (NON-FAP) that has never returned fantastic fuel economy. It has always had an issue with black smoke on acceleration. I have blanked off the EGR valve at the inlet end and this has reduced the smoke slightly, although the fuel economy only ever returns 27-29mpg around town and on a long motorway journey never gets above 30mpg. I know black smoke is the sign of unburnt fuel, but can anyone recommend what I look at next in an effort to a) reduce the smoke and b) improve the MPG. I have also had the codes read and there is nothing logged to indicate a problem.

Thank you for your help/advice in advance

[Hell Razor5543]

Sometimes the black smoke is due to a dirty air filter/clogged filter box. Poor air quality has that effect. It could be worth checking/changing the filter, and see if it helps.

[SaabC5]

Try unblanking the EGR valve and then spraying some Wynns EGR valve cleaner down the pipe to the EGR whilst it ticks over. Do it in short sharp bursts or the engine will stall on you, also spray in the opposite direction towards the manifold. I'm sure you will find loads of black gunk/residue in the pipework thats burning constantly.

[wheeler]

Hi all. I have a 2006 Citroen C8 2.0Hdi (NON-FAP)

Is this a UK spec car ? I thought all diesel C8's had FAP/DPF ?

[SaabC5]

I thought all later models 03 onwards had a DPF. My 2.2Hdi has and thats an 02 model. I was under the impression the early 8v model were non DPF and all the 16v had one.

[oneday]

8v are none dpf it arrived on the 2.0 with the 16v late 04 facelift model

[Peter.N.]

Surprisingly there is a 16 valve 2.0. with no DPF - I looked it up.

Peter

[bradspau]

Hi it definitely has no particle filter. Anyway, I have tried the Wynns EGR cleaner in the past and it didn't do much. I tried it again this weekend up the inlet pipe, with the blanking plate off. Again, it didn't make a massive amount of difference, however I have left the blanking plate off now and although it is still very smokey, it doesn't seem as black and as dense as it did with the blank in place. Anymore ideas would be welcomed thanks!

[Bick]

hi there, you say you have had the fault codes read was this with a lexia?

Have you tried running a few bottles of fuel system cleaner though?

Auto or manual?

milage?

weekly milage?

supermarket fuel or not?

sorry for all the questions but we will need this information, i would say you are aprox 10 mpg down.

[bradspau]

Fault codes read with lexia nothing logged. Manual gearbox, 85000 miles, weekly miles approx 200 and generally supermarket fuel although I have tried a few fill ups with shell, to no avail. I have tried redex in the tank and injector cleaner.

[miked]

Surprisingly there is a 16 valve 2.0. with no DPF - I looked it up.
Peter

I have also seen references to non DPF C8 HDI's, but always assumed they were not UK models.

Fault codes read with lexia nothing logged.

Did anything show up strange on the live parameters with the lexia?

We don't have any black smoke from ours, So something is wrong with yours but the fuel consumption figures in your first post are similar to what we get. It is a very heavy car (1.75 tonnes), shaped like a barn door. On a good A-road run at 60 mph it will get over 40 mpg but depending how much you push it on the motorway then 30 mpg might be about right. We always try to aim to get 600 miles from a full tank. (it costs £110 to fill)

[bradspau]

I never got the live data read, so I guess I am going to have to take it somewhere to be looked at In the last post, my figures on a A-road or Mway at a steady 60mpg constant still only returns ~30mpg...I would love to get 40mpg but that has never happened.

[bradspau]

I am still not convinced removing the EGR blanking plate has made much difference. Would you guys recommend blanking it off again, to save further problems. Due to the location of the EGR valve on this engine being almost impossible to get at, I put the blanking plate in the EGR inlet pipe that feeds off the manifold just after the air doser. I assume this would have the same effect as putting the blanking plate under the EGR itself. Also, once blanked off what do you recommend doing with the vacuum hoses?, leave them connected? blank them off?

Also this model has an auxiliary heater which as I understand is there to help warm the engine up quicker, it has a small exhaust outlet underneath the car and the fumes from this are rather smelly. Is this normal? Would the auxiliary heater effect the fuel economy?