throttle body sucking oil from the valve cover via the breather hose into the engine .when i pull off the hose with the engine running there is heavy sucking of air into the TB. valve cover and pcv valve only weeks old . When oil from the valve cover gets into tb, vehicle smokes Can anyone say why would the throttle body would sucking so hard that it pulls in so much oil? my car is 2008 vaUxHALL astra h 1.6

EDIT (added from other post - PLJ):

I want to believe that there is a leak somewhere as my mechanic has blocked off the breather hose and the car runs very good .it throttles okay ,responds to the gas pedal perfectly .no pressure the engine ,the dipstick is not sucking nor the filler cap.Mechanic said the breather hose on the TB was sucking the life out of the engine. But the engine must be breathing from somewhere dont?. On the other hand it be electrical ? i have plugged off the MAF sensor and no change to engine it seems bad or the tps . I have not seen any check light though.it seem im burning a little more gas too.

  • Is your air filter blocked?
    – Solar Mike
    Commented Sep 26, 2017 at 6:57
  • Possible excess oil in the engine? Perhaps an air leak elsewhere in the engine generating a high velocity of air picking up oil along the way? Oil fill cap sealed? Dip stick sealed? Or possible leak at head gasket allowing compression gasses to push oil? I'd like to see the results of compression test on each cylinder.
    – zipzit
    Commented Sep 26, 2017 at 8:01

3 Answers 3


There shouldn't be "heavy sucking of air into the TB" when the hose is disconnected unless your air filter is totally blocked. Try removing your air filter and retest. However, excessive crankcase pressure can cause oil to be pushed out of the breather and into the throttle body. This can be caused by worn rings or worn valves, oil sloshing (hard cornering), or too much oil in the crankcase.


The simplest answer to all this is to replace the valve cover and which is cheaper when you buy it online ,and it is also cheap to replace it yourself you don't need a mechanic. The other way is to buy the pcv valve and replace it.The valve is located inside the top of the cover but it not easy to remove due to all the heat of the engine, and note these parts are plastic hence I recommend replacement of the cover, which is much easier.


Throttle Body and Intake Manifold A bad PCV can cause excessive oil to accumulate in the intake and throttle body. First check for bad vacuum lines. Second replace PVC. Third, check vacuum pressure and make sure the needle on the vacuum gauge is not bouncing. Fourth, check cylinder compression in each cylinder. Fifth, make sure the intake manifold gasket is not bad. Sixth, make sure you have a good air filter and all vacuum line's are connected properly. Seventh, make sure the intake air control valve on the throttle body is working properly. Eighth, properly clean the throttle body and replace the throttle body gasket. Ninth, make sure there are no other bad engine gaskets. Finally, use a head gasket test kit to make sure the head gaskets are good. If the head gaskets are good, the test kit die should stay blue in color.

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