TD4 Diesel:
New air and oil filters, clean oil, new vacuum hoses, MAF cleaned and EGR blanked off.
Car starts no problem with just a puff of smoke. Accelerates up through the gears without any problems.
Decelerating through the gears and then hoofing it does not result in a cloud of smoke.

But, on one, and only one, occasion this week I was checking for air leaks with the engine ticking over and it started to smoke a bit.
A few minutes later there were clouds of blue smoke every time I blipped the throttle.
Took it for a drive and the smoke cleared after 1/2 mile, but it was VERY bad at the beginning.

The problem has not recurred, but what could be the cause?

Mine makes blue smoke if I hold the revs high for a minute or so. It only does this under light load, so I suspect it's oil being thrown from the turbo.

It doesn't take much oil in the intake system, to produce lots of blue smoke.

Nodge68 said:

Mine makes blue smoke if I hold the revs high for a minute or so. It only does this under light load, so I suspect it's oil being thrown from the turbo.

It doesn't take much oil in the intake system, to produce lots of blue smoke.

Click to expand...

Change the crankcase filter to the new sort:

And then clean out the intercooler of oil contamination:

From my experience. The cotton wool type filter is better at keeping oil out the intake manifold.

Found the crankcase filter mod already done when I change the air filter.
Looks like it may have been oil in the intercooler. As per the second video I'll take it out and clean it and the rest of the duct/pipes..

I’ve eliminated crank/turbo oil as a source of smoke. Now I just have white smoke when holding the revs in neutral at 2500 rpm. If I force the turbo control solenoid to come on (cut the control wire and ground the one going to the solenoid so its filly engaged) full vacuum goes to the turbo actuator and the control arm moves to its full extent and I get no smoke. So problem was not enough air going in. And solenoid, actuator and turbo presumably ok. But if I leave the ECU to drive the solenoid, then it smokes. I can see that the ECU is driving the solenoid a bit as the actuator arm moves a bit, but not as much as when I manually force the solenoid on.

What do people think is causing this?
Should the ECU operate in a closed loop mode monitoring the boost via the MAP sensor and keep on driving the turbo solenoid on until enough boost pressure is reached? Or does MAP pressure not affect the drive to the solenoid?

- Turbo hoses and vacuum lines - can’t see any splits. I’l do some more vacuum tests on lines. And try and pressure test hoses/intercooler.
- Tested MAP - seems to output the right voltages at different pressures. So looks ok.
- Tried two different MAFs - no different
- I am getting some boost pressure, but more boost when I manually force the turbo solenoid. Has anyone got any boost pressure readings on a good TD4 at 2500rpm in neutral? (Or MAP output voltage)

Maybe the exhaust is clogged limiting turbo spin, but it revs fine to 4800 rpm and no smoke over 3500 rpm so probably not this.
Injectors have all been stripped, cleaned and tested. Leakback test ok.
LP pump changed, HP pump regulator seals done (were worn) and now the HP fuel sensor gives correct voltage (hence ok fuel pressure) around 2v at 3000rpm

Starting to run out of next things to check.....