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I have an Alfa Romeo 159 Sportback 1.9 JTDm 16v. Recently a warning message appeared stating "Pollution Filter Clogged". The garage tells me this happens if the car has been driven at low revs in traffic for a while, and to trigger the self-cleaning process I need to drive down the motorway at higher revs for a while to get the exhaust and filter up to the required high temperature. So I went for a drive down the nearest motorway holding it at around 4,000rpm in a lower gear. After 45 miles it still hadn't triggered the self-cleaning process and I ran out of time. It looks like I'll have to have another go (maybe 55 miles will do it?) I'm sure you'll agree that whatever benefit is derived from these filters is more than cancelled out by burning off fuel at high revs for 100 miles of unnecessary driving. How do I know if it mightn't be just a faulty warning signal and it doesn't really need cleaning? Do you have any experience of this problem?
Asked on 5 September 2009 by
Answered by
Honest John
DPFs work ‘passively’ the way you describe. They may also work ‘actively’ when what is supposed to happen is a separate fuel injection nozzle in the DPF supplies neat fuel to burn off the particulates. Watch the instant fuel consumption meter and you will notice a sharp increase in consumption when this is happening. But if these don’t ignite, the neat fuel runs back into the engine sump, contaminating the sump oil and can raise it to the level when the engine runs uncontrollably on its sump oil until it self-destructs. The latest ‘Closed Loop’ DPFs, fitted to some cars from about 12 months ago, don’t allow this to happen.
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