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Hi there,

It seems after reading about the D4 VVTI engine:
https://www.aa.co.nz/cars/ask-an-expert/faults-reliability-service-and-repair/show/5386/
our 2004 Toyota Avensis (200km) is possibly experiencing some of the issues discussed in the forum with carbon-build up.

The car seems to run fine, but over the last six months it has developed a 'whirling' sound - best described as the sound made when paper hits a fan. To my knowledge the sound is constant when over 1200 rpms. I have had a listen and a play around when the bonnet is up and from what I can see, its not a loose mount or heat-shield and it seems more internal when you are driving if that makes sense, which is why I am leaning towards the carbon build-up.
The car been run on high-octance since we purchased and has had regular maintenance in the 5-6 years we've owned it, (these issues have never been bought to my attention either) but to keep costs down in last year, I've done the basic service stuff myself (oil/oil filter change and top-up and air filter.)

Firstly, I was wondering, is cleaning the valves and cylinder head a major job that any reputable mechanic can undertake or is it more of a specialist activity?

Secondly, I am not a car person, so what happens if this particular issue isn't solved? Does it just affect performance, economy etc or does the engine eventually seize up.

Thanks in advance

Hi there,
It might pay to have the vehicle looked at by a mechanic just to make sure nothing more serious is going on. I wouldn't have though that a noise would be associated with a carbon build-up inside the engine intake manifold. Cleaning out will depend on how deep the carbon extends, in some cases the cylinder head needs removing and placed in an acid type bath to try and clean it out. I think the symptoms are mainly in the area of poor performance or rough operation. There are a few things worth checking, like drive belts, transmission, or power steering system that might need closer inspection.