DPF problems on my 320d E91 HELP!

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DPF problems on my 320d E91 HELP!

Postby emver » 09 Oct 2017, 16:35

My E91 320d suddenly started running roughly at low revs a while ago. The fault seemed to clear itself but came back again, and this time the DPF warning light came on briefly. The car has done 129k miles but since I bought a 520d a year ago I've only used the 320d for short journeys. This seemed to point towards a partially blocked DPF.

I took the car for a 40 mile motorway trip hoping to initiate a regeneration but it didn't work and the car now runs even worse, very rough and lumpy at low revs although it still starts and feels a bit better at higher revs.

I then made the mistake of taking it to Halfords for a DPF deep clean and forced regen. This didn't work either. They claim to have injected the cleaner directly into the DPF then unsuccessfully tried to force a regen. After this they did a diagnostic test which said that the exhaust differential pressure was too high (or the sensor was faulty), the MAF was faulty and one glow plug was faulty. In my opinion they should have done the diagnostics first, and if they thought it was unlikely to regen the they shouldn't have wasted my £85 for the DPF clean.

Now for the faults they discovered. The MAF probably showed as faulty because the DPF is partially blocked which would have affected the air mass readings. A faulty exhaust pressure sensor could be the cause of the original problem if it is preventing regeneration, so I've replaced it. Nobody seems to know for sure whether a faulty glow plug will prevent regeneration. I've read that it will do, but a local indy who is BMW trained is sure that it won't. I did try to replace the plug, but on my model the plugs are buried beneath the inlet manifold and that seems to be a massive job to remove. Besides which, the indy tells me that I'm very likely to snap the plug in the process, which would mean cylinder head removal.

So now I have 4 choices:

1. Take the car to the local Indy and let him sort it out. I'm a bit reluctant to commit to more indeterminate expense with no guarantee of a solution, especially if he's wrong about the glow plug. On the other hand he has better diagnostic equipment and a lot more knowledge than I do.

2. Replace the DPF. A new one is available on ebay for £218 which is a lot less than I thought, but I don't fancy the job of fitting it. As yet I haven't found anybody in the Coventry area who will fit it at a reasonable price. Any ideas anybody?

3. Have the DPF removed and cleaned off the car. Gap Turbos in Birmingham offer this service and it might be my cheapest solution, but the car might still not regenerate if I there is a fault preventing it.

4. Continue to puzzle it out myself. I've ordered some fancy looking software through Bcables on ebay so hopefully this will give me more detailed diagnostic information, and enable me to carry out a forced regen. That's assuming I can work out how to use it of course.

Any ideas or well informed advice would be very much appreciated.
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Re: DPF problems on my 320d E91 HELP!

Postby M60NJP » 09 Oct 2017, 16:43

Not a well informed view from an e91 perpspective, but a customer of mine has been through the same thing with a Volvo and currently has a bill of over two grand.

If the DPF is blocked, chemical cleaners are pretty much useless (they're OK if used pre-blockage or when the blockage is minor...which is rare)...unless you need a quick fix for an MoT or selling the car!!

The remove and super-heat option doesn't get good feedback (to my ears) - said customer had it done for close to 70% of the replacement cost....and ended up with a replacement anyway.

I'd go for the replacement option - but would steer clear of an Ebay one. Take it to your indie (or bring to mine, I'm only 45 mins away in MK) and let them replace and code it.

The MAF can soot up if the DPF is clogged, so could need cleaning. Can't see the relevance of a faulty glow plug to the DPF, but if it needs a new one, it needs a new one and they're (relatively!) inexpensive so get it done at the same time!
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Re: DPF problems on my 320d E91 HELP!

Postby emver » 10 Oct 2017, 08:48

Thanks for your reply M60NJP. I'm curious as to why you would steer clear of a new DPF sourced on ebay? Are you saying that an indie would be able to source better quality DPFs, and if so why?

Perhaps you have missed my point about the glow plug. A lot of people think that a faulty glow plug will prevent regeneration, and if they are correct then I need to replace it. But on my model that would involve removing the inlet manifold which would be an expensive job, as well as running the risk of snapping the plug with all the problems that would bring. The car starts fine so my choice would be to ignore the faulty plug, unless it really is preventing regeneration.

Does anybody know where I can find an authoritative answer about whether fully functioning glow plugs are a necessary precondition for DPF regeneration?
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Re: DPF problems on my 320d E91 HELP!

Postby M60NJP » 10 Oct 2017, 09:12

emver wrote:Thanks for your reply M60NJP. I'm curious as to why you would steer clear of a new DPF sourced on ebay? Are you saying that an indie would be able to source better quality DPFs, and if so why?



I can't comment generally as I haven't seen the Ebay ad, but generally speaking things are cheap for a reason and most car parts come in a range of quality - sometimes it doesn't matter, sometimes it does. My local indie can be relied upon to use good quality parts, and I suspect most others do.
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