Engine Smoke Problem

[Smokie]

I'm going to need someone who really knows the 2.0VVTi to help with this one.

What could be causing a large cloud of black/grey smoke to suddenly blow out of the exhaust when the engine hits 5000 rpm under maximum load? Below 5000, nothing. Then as the needle touches 5k, the smoke cloud erupts. Change down and smoke goes, still on full throttle. On part load its clean all the way to the 6000 cut out. Its worst in 3rd gear pushing full power up hills. Two dealers have drawn blanks and deny there's anything wrong, although one did download a software update which helped as it was smoking at 4000 rpm before. Its had a new lamda and, recently, a new cat, all under warranty. Emissions tests prove its in fine condition and it runs smooth and powerful. Oil consumption (full synth) is just over 1L every 10K and it averages over 35mpg in hard use. I've had it a year and covered 45,000 miles in that time (now on 85K), 95% fast motorway stuff and it's always done this. Recently I drilled holes in the lower airbox in case there was an airflow restriction - that didn't help with the smoke but it did give a huge improvement in mid-range wack which is just as well as I can't push it hard at over 4,800 rpm without disappearing in a huge smoke cloud.

[funkyg]

I get a little bit of smoke around 5k revs, I thought it was probably a bit of unburnt fuel and normal. I've seen quite a few sports cars do this, nothing until they floor it and then loads of grey smoke.

Mike.

[Ringthane]

If I was to make a guess at a diagnosis, I would say that you are getting oil from the hydraulic system used to vary the valve timing, into the intake valve. This is based on the fact that you only seem to get the smoke when the long duration cam kicks in. However, I have never studied the cam arrangement in detail so i dont know if there is a direct path for leaking oil from the vvti actuator into the intake valve.

[Smokie]

If I was to make a guess at a diagnosis, I would say that you are getting oil from the hydraulic system used to vary the valve timing, into the intake valve. This is based on the fact that you only seem to get the smoke when the long duration cam kicks in. However, I have never studied the cam arrangement in detail so i dont know if there is a direct path for leaking oil from the vvti actuator into the intake valve.

←

Thanks for your comments, Ringthane. I'm inclined towards the problem being major over fuelling at that point by the management system but can't figure out what makes the ECU think it needs to suddenly squirt a extra load of fuel into the cylinders. It's as Mike says, unburnt fuel and soot from an over-rich mixture except a lot more so than could be considered normal. Spark plugs & tailpipe quite sooty. Following cars drop back when they see it as it looks like a blow-up!