Q: Oil cap is under a vacuum.

asked by on February 25, 2017

My fx4 started rattled very badly. It stumbled and popped and stalled. It would not restart. 45 minutes later it started with a rough idle ( very poor) and loud humming sucking noise. The oil cap is very hard to get off at idle. When it comes off the truck stalls. The tube from the pass. valve cover to throw the air box is the loud sucking sound. I took off the pcv tube at the intake and put my finger over the hole and the humming stopped but sucking problem still excists. Please any ideas. Thanks so much in advance. Mike

My car has 170000 miles.
My car has an automatic transmission.

The vacuum is due to the (PCV) Positive Crankcase Ventilation valve being plugged up. I recommend replacing the PCV valve and the issue will go away. When the PCV valve is plugged up, the engine crankcase cannot breathe and causes the engine to create mass amounts of vacuum internally. If you need further assistance with your oil cap not coming off, then seek out a professional, such as one from Your Mechanic, to help you.

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