C5 2.2 HDi excessive smoke under acceleration

[Orbit Motors]

Sorry, bit of a long explanation...

Hi everyone, currently on holiday in my trusty 2006 C5 with the 2.2 HDi engine. Before going away I'd had a couple of issues with a randomly appearing ESP/ASR fault which had absolutely no pattern to it at all. It seemed to settle so I left it. It has also always smoked quite a bit under hard acceleration (black). While in Germany on our way to Poland, after the fourth time of the light coming on and severely restricting the car's capabilities of accelerating, I decided to try and unplug the MAF sensor to see if it would keep the warning at bay as I had a feeling it would have something to do with that.

As expected I had an engine management light but I knew what it was regarding so I wasn't fussed. Unplugging the sensor kept the ESP warning at bay at the expense of being unable to use cruise control, but at least I had full acceleration back. While in Poland I've ordered a new MAF sensor as parts are generally far cheaper here, and I've fitted a replacement genuine Continental one for around £80. The warning has since stayed at bay and the EML has extinguished so I'm assuming that was the faulty part.

Now though, it seems as though it is smoking even more than before under acceleration, particularly if you're in a high gear on a motorway going uphill for example. There is a noticeable flat spot in acceleration where the smoke appears worst. I'm not sure if it is because the car is absolutely wedged with luggage and I've just not noticed it when working it hard before or if something more serious is developing.

No other unusual signs of a problem. Serviced it a couple of weeks ago and it has done around 2000 miles since, oil was the correct recommended type of Total Quartz. It doesn't appear to be burning oil or anything like that. No other warning lights or messages. Obviously no access to Lexia just at the moment.

Unrelated information of note however is this car is unbelievably excellent at everything, particularly navigating poor and often unpaved road surfaces in Eastern Europe and the cobbled potholed country lanes are ironed out perfectly by Hydractive. I want to keep her going!

Many thanks in advance for your suggestions.

[Rp0thejester]

What's the mileage? and has anyone messed/altered the DPF in anyway?

[mickthemaverick]

Having replaced your MAF sensor have you checked the air filter is not clogged ?

[Orbit Motors]

Mileage is around the 135k mark. Not aware of any DPF changes but then again I haven't examined it.

The air filter is brand new, meant to say I changed that at the same time as the oil a couple of weeks back.

[Rp0thejester]

Is the smoke from the exhaust still black under acceleration uphill? Or white?

[mickthemaverick]

Black smoke from a diesel is generally due to an over rich mixture - two basic causes are not enough air getting in or too much fuel from one or more injectors. Having replaced the air filter make sure the ducting isn't concealing a leaf or crisp packet or similar. If all ok the next best step is a proper diagnostic and injector test. Of course you may have an issue with the EGR or turbo too but I'd start with the basics

[Rp0thejester]

I was thinking the same Mick, over fuel through the EGR would give white smoke, black smoke can't be oil as that's blue, black smoke is not enough air or someone has tampered with the DPF, as in drilled holes through it

[Orbit Motors]

No white smoke at all, that would cause a bit more alarm to me in honesty! When I get home I'll do some more investigating. Is there a way of checking whether my injection pressures are correct by using Lexia or would this be a leak-off test job?

[Rp0thejester]

White smoke would indicate over fueling so EGR issue, if no white smoke it should rule that out. The fact it's black smoke makes me think that someone has drilled holes through your DPF

[Orbit Motors]

White smoke would indicate over fueling so EGR issue, if no white smoke it should rule that out. The fact it's black smoke makes me think that someone has drilled holes through your DPF

Interesting. Are they easily accessible on these? Sorry for the daft questions but I only bought this car on the cheap as a "get out of jail free" while my C6 was in the garage and it turns out I actually quite like it, so other than changing the oil and filters and sorting out an issue with the screenwash tank I haven't actually been underneath.

[PaulC5]

On our cars with a dpf I have found the inside of the exhaust tail pipe is clean metal. If your dpf has been drilled through it might be covered in soot. I had a petrol Saab on which the turbo failed on the M6, it surrounded the car in white smoke so I stopped and called the RAC. It was also a bit noisy before but for a few months there was some blue smoke on starting and accelerating.

[Rp0thejester]

Worse case, to many forced regenerations could have destroyed the DPF and made it crumble into pieces. I don't think that's likely. It's easy to get access to underneath. If holes have been drilled through the DPF it would allow the soot and ash exit the exhaust without being cleaned, hence the black smoke. OR it could of had a new Dpf and the EGR is kicking out soot which I doubt. Accelerating uphill and more black smoke says to me the DPF has been drilled through.

[Rp0thejester]

Messing with exhaust systems and blah blah that help the environment are illegal. But if you didn't do it/have knowledge of it when you got the vehicle, your okay

[aspire_helen]

DPFs are extraordinarily good at catching virtually all soot/carbon. My understanding is that it would still stop any/all soot produced by over-rich injection, the filter would just clog that much sooner. If it has "always smoked black" I would agree the DPF has failed (possible, but unlikely over-heating) or has been purposely "deleted" in one way or another. I assume you have not had it MOT'd since you owned it? If deleted, the ECM would measure a zero pressure drop across the absent DPF as a fault (eg a legitimate "filter punctured") and flag up a pollution/DPF warning....so I assume the ECM has been re-mapped as well. Lexia will tell all.

[aspire_helen]

PS Now I have one, I will be taking my Lexia laptop on all trips. I have had "spurious" brake/ABS/ESP fail warning twice in the last 1000miles or so, which of course disables the ABS. Lexia recorded both as "temporary faults". The first warning disappeared after re-starting the engine. The second was more persistent, but I cancelled it with Lexia. I do 2 one-week trips to the Lakes in December and January. It would be annoying to have to live with a spurious ABS failure knowing that it could be reset "if only I had my Lexia with me".