hi all my 06 td4 has a bad smoking problem so bad its off the road I had the injectors tested one faulty so fitted recon one today started up no probs for about 10 mins then smock and running rough really bad smelling of fuel so I disconnected the fuel rail harness and the rough running nearly stopped smoother idle with the plug off plug back on worse again off or on still smokes so would I be right in thinking I need this rail harness and maybe the sensor as well ? would this problem cause this smoking problem

What colour is the bad smoke? I had a similar problem with Black smoke, and lots of it. It turned out to be the air temperature sensor on the short hose right at the front of the engine on the air intake. Take off the plug, spray with switch and contact cleaner, then VERY CAREFULLY close the gap on the plug terminals using a small electrical screwdriver, then refit plug. this simple fix totally stopped my smoke issue. Fingers crossed for you.

Hi its blue white really bad smelling like a old smoky bus its not oil smoke the temp sensor is working it shows on my scanner iv just changed pcv unit it has the bmw mod still the same the engine starts and runs sweet for a few minutes then the smoke appears. once it starts to warm up it starts to run rough unplugging the rail sensor stops the rough running compression must be ok as it started ok today with no heater plug light on iam running out of ideas I am now thinking about the rail harness £42 from LR should be free I am not getting any black smoke from the car if I hold the revs a 2K the smoke gets horrendous and miss fire and the smell hangs in the air and around the car

blue smoke is oil ,can be caused by poor injection as well as common issues like valve seals and worn rings etc,might be worth checking egr

No EGR fitted the injectors were tested one was slightly faulty recon one fitted the car uses no oil and the engine had good power. if it was valves or rings or poor compression it would smoke as soon as it starts last night it was smoking then stopped for 5 mins then started again I drained the fuel tank and put fresh fuel in as well ? why would the engine run better at idle with the rail plug off iv checked for fault codes nothing thanks for the reply