2008 Audi A4 Quattro. Runs super well, but starts surging and choking when brought down to idle. Rather than spending days chasing this vacuum leak around the engine, can I just manually close the vacuum port on the throttle? Unplugging the PCV line and doing so manually with my finger completely fixes the idling issue, so I'm wondering if the system is only really necessary for emissions stuff. Would it hurt anything to put a piece of electrical tape over that and call it good?
Any tips on the subject for bypasses or chasing this vacuum leak appreciated!!
Thanks
Yes.
Without the PCV system, the pressure inside the crankcase will cause oil to leak out of places it ordinarily wouldn't.
Second, you'll build up sludge inside of the engine.
Fuel economy also suffers if the crankcase is under pressure, not vacuum.
Make sure that the dipstick tube isn't broken, the oil filler cap seal is good, etc.
In reply to Pete. (l33t FS) :
Would the valve cover gasket do it? I have heard they are a one-use thing on these cars and I have removed that once before but never replaced the gasket. The engine runs substantially worse when you remove the dipstick/fill cap, making me think its a small leak. Will check both for leaks.
I changed the PCV on my Locost to just a filter when I went ITBs.
It leaks oil all over the place, and the oil goes pretty black and stank within very short order. I'm going to hook it back up some time.
My 1200 has no provision for a PCV valve due to ITBs. The block vents into a catch can.
Granted as a race car it sees very few miles relative to a street car but I've not experienced any ill effects.
On a newer street car I'd take the time to track it down.
Leave the PCV system and change your oil every 5000. Remove the PCV system and change your brown pudding every 2500. It's not that apocalyptic, but the PCV system does WAY more than most people think for oil health, emissions, ring seal, leaks, MPG, etc.
Thanks for the replies everyone
I intend to daily this car, so after doing some research just bypassing seems like a bad idea.
One of the ways to check the system is remove the oil fill cap with the engine running, if there is suction and the engine starts running crappy the PCV is good. If there is no suction and the engine keeps running poorly as when the cap was installed, the PCV is bad. My car has the symptoms of a good PCV, idling even worse with the cap removed and pulling good vacuum.
This make me think the vacuum leak is minor, only prevailing when the engine is at idle and building the most suction. As soon as some throttle is applied it clears up completely. I will start with the basics, checking the dipstick, oil fill cap, and maybe the timing cover gasket? I removed this once before without replacing the apparently one use gasket, could this be where the leak is coming from?
In reply to Curtis73 (Forum Supporter) :
I get about 1000mi in my PCVless car before fuel dilution makes it a quart overfull. And I only fill to the add line when I change the oil.
The companion car does not do this, because its PCV system is intact.
In reply to Pete. (l33t FS) :
I got my 383 in the boat several years ago and didn't have time to come up with a solution for PCV with the valve covers I had on it. A similar thing happened to me. At the end of the boating season I drained out about 6 quarts of pretty thin, diluted, fuel-smelling oil. I made it a priority to figure out the PCV
