Seeking Advice on '04 Mazda Premacy Diesel Issues: Black Smoke, Check Engine Light, Power Loss and DPF Regeneration Failure

Hey there fellow gearhead, I've had a somewhat similar experience with my '02 Mazda6, not exactly the same model but close enough. Now, I'd say I have some experience with cars, it's more of a hobby than anything, not a pro by any stretch. It sounds indeed like you might have a problem with the EGR system. The same black smoke and strange hissing noise led me to the garage to get my car checked and like yours, it ended up being an issue with damaged cables on the electric changeover valve. Cost me 155€ to have it fixed, pretty reasonable I reckon. By the sound of it, you're experiencing more severe symptoms though. It could be possible that your DPF isn’t regenerating due to a failing sensor or fuel additive system problem? Could you share more about your car's mileage and maintenance history? That would help narrow things down more precisely. And remember sometimes it's better to let the pros handle this sort of thing, no shame in that!

Hey, cheers for your insights! My Mazda Premacy's on the higher side of the mileage spectrum, currently clocking in at 258191 km. The last service, just a routine check-up, was not too long ago. I guess you're right, might be time to take her to a professional, a dodgy sensor causing the DPF to fail sounds plausible. Never had an issue with damaged cables on the electric changeover valve before, but that's worth a check too. Your help means a lot, hope to get her puffing less black smoke soon. Thanks again!

No worries happy to help a fellow Mazda owner! With the kind of mileage you've got on your Premacy, it does sound like a sensor could be on the blink, causing your DPF to fail. Also, given the black smoke and drop in power, it wouldn't hurt to check the air filter as well, it might be seriously clogged. Though I'm fairly sure your mechanic would look into that during the routine check-up. And remember the issue with the eletric changeover valve I mentioned earlier, it didn't give me a check engine light or DPF fail warning. So yes, it looks like your issue could be more linked to the DPF sensor. Hope you get her sorted soon. Do let us know how it goes. Always good to learn from each other's experiences! Cheers!

Thanks again! Will definitely have them look into the DPF sensor and I'll bring up that electric changeover valve issue for good measure. Airfilter check's definitely on the list as it's been ages since I last replaced it. Just hoping it won't cost me an arm and a leg! Your advice's been invaluable, and I'll for sure post an update once I get to the bottom of this. Cheers, and keep revvin'!