I have a 2000 Civic Ex Coupe standard trans. I have been having issues lately of intermittent power losses. The only way to describe it is if I am accellerating and repeatedly tap the clutch… that’s what it feels like… but I’m not touching the clutch. Then, when I pull the dip stick there is suction in the engine. Doing that seems to fix it for a minute. But, it is happenning more often. Any thoughts? Thanks in advance for any advice.
Are you pulling the dipstick with the engine running? In either case I think you have a bad PCV valve. Check it. Does your engine use oil or smoke?
The engine is off when I pull the dip stick. The car does use a little oil. I will check on the pcv valve.
The engine should not hold a vacuum when the engine is off. The pcv valve has to draw in fresh air somewhere through the air filter. You need to take off the air filter and find the component that’s plugged up. The pcv valve is probably sticking also.
The PCV valve is SUPPOSED to provide a vacuum to the crankcase to prevent pressure build-up forcing oil into the combustion chambers.
As I understand it, the PCV valve is a one way valve (check valve) that allows fumes to be sucked out of the crankcase and fed back into the intake manifold to be run through the engine (again). But it blocks backflow of fuel rich vapor when the pressure in the intake manifold is higher than the crankcase. All that means that the crankcase does indeed operate with a slight vacuum.
But I believe that there is a separate, unvalved hose that cycles air from the air intake to replace the fumes and air being sucked out through the PCV system. The presence of that line normally presumably keeps the crankcase vacuum slight – which it is in most cars.
If the PCV system really works the way I think it does – and it might – then I’d find that second air hose and check it for blockage.
Thanks vt. The engine does not hold a vacuum when the engine is off because the fresh air inlet is not a one way valve. Vacuum is only there when the engine is running.