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I have a mazda 3 sport diesel on a 07 plate it has 133000 on clock, I bought this car a couple of months ago and have noticed a lack of power in the lower gears. it struggles to overtake unless I have some momentum going but when I do get some speed up it seems ok. I have had it in a garage who have tried to do a forced re-gen but could not overide the code on the diagnostics machine, there is no dpf light showing and I am now thinking do I get rid. I do a 90 mile roundtrip to work regularly and find it very frustrating when sitting behind a slower vehicled and cant overtake unless I have a very clear road ahead, any ideas?

edboo
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3 Answers3

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The DPF is a very likely problem if you lose large amounts of power, though if you do 90 miles daily then DPF should have no problems regenerating without intervention. There are other problems that could cause a significant lack of power on diesels (if there is no check engine light on):

  • A really dirty air filter that needs replacing;
  • A clogged fuel filter (already mentioned);
  • A blocked EGR valve that needs cleaning;
  • A turbocharger fault, like a stuck wastegate, faulty boost sensor or mechanical failure;
  • Clogged exhaust causing backpressure, most likely at the catalytic converter;
  • A faulty/dirty MAP/MAF which fails to calculate required fuel, should be accompanied by poor idle and/or clouds of black smoke out of the exhaust;
  • A faulty temperature sensor that forces the engine to run in "cold" conditions, the gauge should give this away if it does not read a separate sensor;
  • A stuck thermostat that does not allow reaching operating temperature, also should be given away by low temperature;
  • Clogged injectors, usually accompanied by problems such as poor idle and difficult starting;
  • A faulty fuel pump, usually accompanied by difficult starting and stalling;

Any other symptoms, like black smoke, poor idle, stuck temperature gauge, stalling?

I have no idea what I'm doing
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  • Please forgive an ignorant question, what does DPF mean? I assume the F = failure or fault, but the rest I have no idea. – cdunn Mar 08 '16 at 15:42
  • When I type DPF into a famous search engine the first thing that comes up is a Wikipedia article on a Diesel Particulate Filter – Ross Millikan Mar 08 '16 at 16:06
  • I agree, that's a great way to go. I have a feeling if I didn't know, others might not either, and putting the answer here, makes the repository of knowledge about this more complete. – cdunn Mar 08 '16 at 17:03
  • @cdunn yes, the DPF is a diesel particulate filter, an often problematic part of the diesel emissions control. If the car is occasionally driven for a longer distance then the filter is regenerated automatically by temporarily increasing the exhaust temperature and burning off the particles as a result. Though many people do short distance city driving only, and some choose to completely remove it from their cars after it starts causing problems, as it is usually cheaper than fitting a new one. – I have no idea what I'm doing Mar 09 '16 at 08:48
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The fuel filter could be dirty, which would be restricting the fuel flow required for acceleration.

HandyHowie
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There could be a split in one of your air hoses from the turbo. This would let out the pressurized air produced by the turbo during boost.

HandyHowie
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