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Tdci Rough Idle, Smoke On Cold Start


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Hi all, first time poster! I have a 1.8 TDCI that I have owned for a couple of months with 104K miles on the clock.

For the past ten days or so it has been idling rough, not bad, just like a very slight misfire. If I turn on the aircon and the revs increase slightly the engine runs fine. During the last ten days I have noticed no loss in power, acceleration or mpg, the car appears to be running as normal.

On Monday it went to a local mechanic who checked it over for air leaks etc and checked the injectors. He said they are running at the correct pressure, the car is showing no fault codes, but he feels an injector is starting to break down but at present he is not sure which one?

Yesterday and this morning the car has kicked out blue smoke at cold start-up and ran rough, just for around 20 seconds and then has cleared.

This is now beginning to worry me! I have a can of BG244E diesel fuel system cleaner that I will try today but I don’t hold out much hope.

Does anyone have any idea of ascertaining the exact injector(s) that are causing the problem, if indeed it is injector problems? I have read some similar threads on here but none seem to have a definitive answer?

Thanks for reading! Any replies would be gratefully received.



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Blue smoke is usually oil burning (at least with a petrol car, diesel might be different but don't think so), black smoke is (excessive) petrol/diesel burning (leaky injectors for example), white smoke coolant leakage into cilinders.

(Have the same with our petrol car, the valve seals are worn and everymorning you start there's a big cloud of blue smoke. But it doesn't run bad or anything, off course it's no diesel so maybe no comparison)

So first make sure it's blue smoke, the color of the smoke defines which direction you have to search for the problem.

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Hi, If this is just on cold start, I would look at glow plugs, if one is down it would make it run rough for a couple of seconds, then run fine, glow plugs only cost around £10 each...glow plug are always over looked.

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I would not advise you to use any liquid to clean the common rail system.

Probably smoke is not blue but white? Try to check the EGR valve, perhaps it is dirty. And do you see a black smoke in the rear mirror during sharp acceleration?

Of course glow plugs should be checked first.

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