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Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 20356
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an s reg a4 1.6 Audi, after driving it approx 15 miles

Customer Question

I have an s reg a4 1.6 Audi, after driving it approx 15 miles it omits a large amount of smoke from the exhaust when the throttle pedal is lifted it will the proceed to develop a miss. The valve stem seals have been renewed and compression test carried out with readings of 150 psi on each cylinder measured turning on the starter not running the engine.engine bores were like new when inspected and it starts and runs without any problems it does take oil but from where?
Submitted: 3 years ago.
Category: Audi
Expert:  Matt replied 3 years ago.

The first thing I'd check is the crankcase pressure relief valve (PCV) these are sprung loaded and are only meant to 'burp' excess pressure every now and then. The exiting gas is piped back to the inlet , however should the valve stick open then the engine tends to suck the air out of the crankcase all the time and this carrys oil over with it.

If you remove the air intake pipe and look inside where the crankcase breather is plumbed in you may find evidence of oil.

If you do find oil replace the valve.

You don't mention what engine this is but if its trubocharged then check inside the intake just after the turbo for any signs of oil as this would be an indication that the turbo oil seal is starting to fail and a replacement / rebuilt turbo may well be required. Have a feel of the turbine wheel - there should be no play radially at all - but a little bit of axial / end to end float is normal

an engine flush may also help if you've got a sticking oil scraper ring so its worth a go, as for the oil if you go up a grade / use slightly thicker oil then this is less readily drawn into gaps and less likely to be burnt off

Customer: replied 3 years ago.

Hi Matt


This block as far as I can detect does not have such a v/v only a rocker cover breather feeding into the air intake through a tee piece with a reduction orifice which enters the intake on the engine side of the butterfly v/v in the throttle body, this orifice I found to be plugged solid though now cleared and oil changed to a higher viscosity the problem of smoke and miss firing remains.

The engine in question as a 1.6 8v normally aspirated unit driving through an auto-transmission ,I think from memory the engine is an AHL model. Sorry I have been so long in getting back to you I have had some family matters to deal with.




Expert:  Matt replied 3 years ago.
Hello Rick

OK in that case I'd suggest disconnecting the breather pipe from the throttle and putting it into a suitable container to give a catch bottle (an empty coke bottle works fine for this purpose) then block off the throttle connection pipe and try driving that aorund for 100 miles to see how much oil you get in the catch bottle as it should be less than 50ml

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