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Too much vacuum. can't remove the oil cap at idle

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All VW cars have what they call negative pressure sumps,that means that the engine is sucking all the air out of the sump at tickover,(its cleaner for the planet ?)try removeing the dipstick,then undoing the cap.(a BMW will STALL if you do this.)

Posted on Nov 13, 2010


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Peugeot RCZ 2010 petrol 1.6 l 115 kw 155 tho. Vacuum when I take the oil cap off when engine is running

NEVER remove the oil filler cap when the engine is running. It will upset the engine pressures and possibly cover you and the engine in oil splatters.
Petrol engines have a negative pressure by design.

May 28, 2017 | 2010 Peugeot RCZ 1.6

2 Answers

Surging while idling and also starting to do it while driving.

Not to sure on the driving bit but on the idle side on the throttle body there is a idle control valve , they are prone on Honda for sticking , u need to remove it and free it up . In the image it's iac valve at the bottom, hope this has helped

Jan 31, 2016 | 1991 Honda Accord

1 Answer

Car says no oil pressure ,with car running l,lots of vacuum when remove oil fill cap ,car dies when it's removed

I suspect two problems. Vacuum when removing oil cap is likely PCV valve. No oil pressure could either be true, and caused by oil pump or clog, or not true, caused by bad sensor.

Nov 17, 2015 | Cars & Trucks

1 Answer

There's hardly any vacuum when you remove oil filler cap when engine is idling

There is not suppose to be vacuum from the crankcase so having none with the oil cap removed is normal.

Nov 11, 2015 | Cars & Trucks

2 Answers

Why on my1997tahoe when you remove the oil filler cap truck will stall and lots of suction

Well -doing that sort of takes out the PCV System
doesn't it

Unmetered air comes in the oil fill hole & gets drawn into
the intake & leans out the fuel mix

You also got PCV system issues with high vacuum

Jul 17, 2014 | 1997 Chevrolet Tahoe

1 Answer

I have suction where i put oil in, when i remove the cap the car trys to stall what do I do? 2002 montero sport limited

You don't add oil with the car running

You broke the vacuum for the crankcase evacuation
(PCV System)

If you have idle problems then they have to be diagnosed

Dec 06, 2012 | 2002 Mitsubishi Montero Sport

1 Answer

98 GMC 5.7L high idle and strong suction on oil filler cap

High idle usually indicates a vacuum leak, you may have one of the smog hoses disconnected, that would also cause a suction at the filler cap because the engine is taking in air pretty fast. I have a 93 2.8l and it will run fast idle for a short time when starting it cold, I have learned that is because it is running rich at that time and the computer thins a rich condition with more air so it is not smoggy.

Unless your throttle linkage is hung up, it is vacuum leak.

Jan 10, 2012 | 1998 GMC Sierra

1 Answer

Engine speed drop

That is normal, when the oil cap is dropped the vacuum to the engine drops also cause the idle air valve to close due to lack of vacuum.

Nov 30, 2009 | 1994 Toyota MR2

1 Answer

94 Toyota 2.4 engine idles fast. when warms up it starts surging

sounds like an Idle air control valve or a positive crankcase ventalation valve(or pcv valve). use some intake cleaner in the air intake and take the pcv valve out and shake it it should rattle and move freely. mike

Jan 05, 2009 | 1994 Toyota Pickup

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