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7 Series DIY
Do It Yourself forum dedicated for 7 Series BMW Owners

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Old 04-09-2010, 08:35 AM
ansirel ansirel is offline
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Location: Turkey
Join Date: Apr 2010
Posts: 1
Mein Auto: E38 740i 1998
Reference - Blue smoke on gas, rocking idle on E38/M62


If your engine, all of a sudden starts smoking in blue (mostly when accelerating) and rocks on idle (rough idleing), this is most likely your torn out CCV (Cyclonic Crankcase Ventilation) diaphragm, which is located on the rear side of your intake manifold.

First check your compession on all of your 8 cylinders. If they give close values to each other in the green area of your compression tester, then you can be sure that it is the CCV. It is a relatively cheap part (less than 100 usd), but replacing it is a nasty job. It is close to the firewall.

The intake manifold must come out for a proper replacement and must be cleaned inside for there surely is a lot of oil in it. This means; covers, spark plugs, injectors must come out. You better get help from a handy friend.

Good luck.

Last edited by ansirel; 04-09-2010 at 08:41 AM. Reason: I survivede the same problem with my 740i M62 engine
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