Smokey Start Rough Idle

Been following the forum for quite some time and now I find myself in need of some help.

2003 Jetta TDI Wagon - 346,000km (217,000mi) on the odometer. Original owner. Only mod is Malone stage 1 tune with dynamic egr and high idle. I am experiencing very smokey (like fog a neighborhood out) cold starts and extended rough idle (which eventually smooths out). The rough idle is stumbly and miss like for say 30 seconds (used to smooth out way sooner).

Car always starts and will sometimes start stall but on second fire up always continues to run. No codes. I have kept up with regular maintenance timing belts, changing oil and filter, fuel filters, air filters etc... religiously. I have recently had it at a shop and all injection values and timing are within spec and good. It has also recently had new coolant sensor and MAF sensor and thermostatic T fitting. Glow plugs have been changed a couple times but not recently - no codes so assume they are functioning.

The car never used to smoke like it does now and its rank. I do have a frost heater and when it is plugged in car starts fine as in not idle rough but still smokes.

Could this be related to worn injectors? Clogging Cat (car is subject to short trips)? Is the high idle or more fuel from the tune contributing to the smoke? Car will use about 1 litre of oil between oil changes (every 8000km/5000mi). Other than that seems to run fine especially when warm.

Thoughts??? I love the car just not this smoke I am being subjected to. I am a multiple diesel vehicle owner and understand they smoke but l have had this car since new and I know it was never like it is now. Valve guides? Turbo or Turbo seals? Compression related (have not checked yet)? Failing injection pump or fuel pick up in the tank? I am lost.

TIA for your help.

If the injectors are original, consider new ones. Running diesel purge straight can help.
Could also be a leak or restriction in the air intake or intercooler piping, clogged intake or CAT. Injection pump could even be snickered.

Thanks for the input. I have ran diesel purge with no real benefit. Intake seems fine but will dig a bit deeper on that one. How can you determine if its the injection pump? No leaks are visible.

Not sure. If the injection quantity is jumping around, that's one sign. Also they can make noise.

Sounds like your pump or an injection line or 2 are loosing prime. Do you see any signs of the pump leaking?

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No leaking from pump that I can see. If it’s pump seals do they always exhibit an external leak?

Are you getting any accompanying lifter noise? Not just a tick-ticking...but, a seemingly out-of-the-top-of-the-engine resonance either?

Compromised little return lines between the injectors will allow air to be drawn into the system when sitting for a few hours.

Thanks. I’ll pay more attention to top end noise and check those return lines.

You may have lifters failing, loosing their prime.

Sounds like your not getting enough air, your intake manifold is likely plugged.

https://www.myturbodiesel.com/wiki/...l-cleaning-of-carbon-build-up-mk4-tdi-engine/

Out of curiosity, what’s your IQ numbers?

When’s the last time that thing got a fuel filter? It’s starting to get cold, and old filters full of water like to freeze and cause crappy cold idle/miss.

I am not sure what the IQ numbers are as the shop didn't tell me. Intake manifold has never been cleaned on advice of shop as they check it regularly and say it is fine. Fuel filter is new less than 8000km/5000mi ago.

Did you ever figure out what the issue was? I’m having a similar issue. It started 6-8 months ago and has gradually gotten worse. IQ is good, just replaced injector nozzles (old ones were CAKED in soot), regular maintenance done, etc. I’m at a loss!