Pull out oil dipstick - a test for vacuum leak?

[phildg2000]

I read in another forum that to test for a vacuum leak, pull out the oil dipstick. If the idle hesitates, this means you have no leak. But if the idle does not change then you have a leak. Moreover, if it turns out you have a leak and the idle does not hesitate, then your engine has been tuned to the leak (how does one tune the engine to the leak? by leaning out with the AFM adjustment?). I tried this on my '89 525i (M20, euro) and there was no change in idle even after I pulled out the oil dipstick. My idling does not hunt but is a bit rough and my acceleration is poor until I hit around 2200 rpm. I suspect a leak. Any thoughts?

Thanks,
Philip

[632 Regal]

sounds like a legitamite test to me, I notice a difference. Also if you have a leak and it is possible for the motronics to tune it out I would also assume you would be burning more oil.

[phildg2000]

Hmmm... so it's the computer thst adapts to the leak. I thought it would have to be physically adjusted to correct for the leak. Anyway, why would it use more oil if the motronics tuned to the leak?

[moots]

my idle's currently good @ 750rpm.mine's also an m20 euro and the idle gets crappy if the dipstick is pulled.i never knew that the system eventually self adjusts itself if there's a vacuum leak?but of crs up to a certain degree i suppose.
there must surely be a leak somewhere in yours then.possible places:
1. inlet manifold gasket 2.breather hose(on valve cover) 3.those small vacuum tubes 4.brake booster vacuum hose..

Try spraying carb cleaner over all visible vacuum hose connections.If the idle changes(rev goes hi),then that particular point is not secure.

[phildg2000]

I will try looking for leaks this weekend