Vac leak under the TB/intake -> erratic idle?

[ortholithiation]

87 325is

Car was a bit rich when I bought it. Multiple PO’s I no idea what has been messed around with. I don’t think this afm has an adjustment screw on it.

Runs rich a bit still, erratic idle 800-1500 for the first 30 seconds, then runs steadish at 1K. (note just had the battery disconnected and reconnected) and this was when cold. But otherwise starts fine.

New plugs- check and gapped at 0.28
Plug wires and coil- check
Distributor- not checked yet
Fixed leaky fuel line
Fuel pressure within spec- check
IAC valve- cleaned and resistance checks out
AFM- cleaned out, checked for binding and resistance increases- check
Intake boot- check looks new
Vac lines to IAC, emission- check, tend to pop out of the TB a bit, so a little rtv was applied, but appear okay.
Haven’t checked the TPS yet, but I hear what sounds like a vac leak coming underneath the TB and intake manifold at idle. Hard to tell from because of the K&N filter and injector noise.
Is this a common problem? I think the breather tube is underneath there as well? Engine seems to rev okay, but running way rich. Also a healthy amount of oil coating all of the intake parts? I’m used to it on a turbo car but on NA?
Going to get some dry ice and fab up a smoke machine, but looking for other suggestions to trouble shoot.

[2.5-12]

here's what mine sounded like with a bad IM gasket: http://www.youtube.com/watch?v=JRocSAnE9Cs

heres what it sounded like after:http://www.youtube.com/watch?v=wDgrhw3sQSM

[ortholithiation]

mines not that bad.

[nando]

http://www.r3vlimited.com/board/showthread.php?t=165760

it's not a breather tube, it's an oil drain from the head to the block. but vac leaks there can cause all sorts of strange problems.

[2.5-12]

http://www.r3vlimited.com/board/showthread.php?t=165760

it's not a breather tube, it's an oil drain from the head to the block. but vac leaks there can cause all sorts of strange problems.

on my M20 the oil return passage is in the intake manifold but has nothing to do with the air intake system.

[SpecM]

on my M20 the oil return passage is in the intake manifold but has nothing to do with the air intake system.

it kind does, a leak here can cause a vaccum leak

[2.5-12]

it kind does, a leak here can cause a vaccum leak

only if the gasket is bad between the oil return and the intake, they are separate, if you hear a leak, its from somewhere else.

I have a picture of a M20B25 IM somewhere I can show you if you need clarification

[SpecM]

only if the gasket is bad between the oil return and the intake, they are separate, if you hear a leak, its from somewhere else.

I have a picture of a M20B25 IM somewhere I can show you if you need clarification

thanks but I don't need a picture, I've taken my intake manifold off before, more times than you have... without the need of post a thread for help, I might add.

the tube is supposed to be under vaccum, from the head, from the breather that runs to the valve cover to the throttle body.

[2.5-12]

thanks but I don't need a picture, I've taken my intake manifold off before, more times than you have... without the need of post a thread for help, I might add.

the tube is supposed to be under vaccum, from the head, from the breather that runs to the valve cover to the throttle body.

just because I wanted to make sure I was going to take it off correctly and have only done it twice doesn't mean I haven't paid attention to how it is laid out. That being said, I did forget that that tube was under vacuum like the top end it is connected to.

I still bet IM gasket on his car though

[agent]

the tube is supposed to be under vaccum, from the head, from the breather that runs to the valve cover to the throttle body.

FWIW, replacing this hose resolved a warm idle issue for me recently.

[nando]

only if the gasket is bad between the oil return and the intake, they are separate, if you hear a leak, its from somewhere else.

I have a picture of a M20B25 IM somewhere I can show you if you need clarification

I know it's not part of the intake air, I said that in my post. it can still cause an oily intake problem.