M42 doesn't like idling

[econti]

So the next thing in my continual series of problems.

I replaced the coolant flange pipe thing the other day. That means intake manifold off, sensors and vacuum lines unplugged, etc etc.

Started it up once it was done, and it runs rough at idle, and doesn't really like idling at all.
I did the spray test on places where gaskets are, and there didn't seem to be a difference.
The PO cleaned up the mess under the manifold.

The only small problem I can see is that the pipe from the rocker cover on radiator end, that joins to some pipes under the manifold, isn't sitting the whole way on to the underneath manifold end. It's on 3 of the 5 ribs. Would that be causing it? I can't get it to stay on all the way.

What have I done wrong?

[Dj Buttchug]

its a vac leak bruh

[econti]

gaskets all seemed fine when it went back together
sort of hesitant to RTV them in case I have to take them off again

[bmwman91]

There's probably a crack in one of the vacuum lines. The stock setup is junk. I used some heavier duty vacuum line and made the connections directly (between valve cover & TB, and intake boot & ICV). The stock molded hoses will crack after a couple months of use, as I found a long time ago. One or two disassemblies will also kill them.

[econti]

There's probably a crack in one of the vacuum lines. The stock setup is junk. I used some heavier duty vacuum line and made the connections directly (between valve cover & TB, and intake boot & ICV). The stock molded hoses will crack after a couple months of use, as I found a long time ago. One or two disassemblies will also kill them.

Will a spray test make them obvious?

And what do you mean, just joining them directly? Could you do a diagram or something? I thought they all had to join together for a reason

[bmwman91]

I don't have any diagrams. It is fairly simple though. The outlet in the valve cover just needs to connect to the metal nipple that comes out the bottom of the throttle body. And the outlet in the bottom of the intake boot just needs to connect to the inlet of the idle control valve.

I have never really had much luck with the spray test to be honest. It works with bigger leaks, but I have always had smaller ones that were found after disassembly and inspection.

It could very well be your intake manifold gaskets. One mistake I made when reassembling was to tighten the 2 steel brackets that secure the upper manifold before the other nuts were in place. Loosen those brackets (both fasteners) and then loosen/retighten the nuts that hold the upper manifold to the lower. Then secure the brackets. If those brackets are tightly in place before you try to tighten down the upper manifold, there is a chance that the manifold won't seat properly on the gasket. Also, tighten the 2 nuts that are higher up on the manifold (on the really long threaded posts that come out of the lower manifold) last.

Did you remember to reconnect the tiny vacuum line between the TB and fuel pressure regulator? That is a common one to overlook too.

[econti]

I don't have any diagrams. It is fairly simple though. The outlet in the valve cover just needs to connect to the metal nipple that comes out the bottom of the throttle body. And the outlet in the bottom of the intake boot just needs to connect to the inlet of the idle control valve.

Ah right, sounds easy enough.
What do I then do with all the metal piping and stuff underneath the manifold? Just leave that there?

It could very well be your intake manifold gaskets. One mistake I made when reassembling was to tighten the 2 steel brackets that secure the upper manifold before the other nuts were in place. Loosen those brackets (both fasteners) and then loosen/retighten the nuts that hold the upper manifold to the lower. Then secure the brackets. If those brackets are tightly in place before you try to tighten down the upper manifold, there is a chance that the manifold won't seat properly on the gasket. Also, tighten the 2 nuts that are higher up on the manifold (on the really long threaded posts that come out of the lower manifold) last.

Will do that tomorrow.
I'm afraid that I did the complete opposite of the way that you described haha.

Did you remember to reconnect the tiny vacuum line between the TB and fuel pressure regulator? That is a common one to overlook too.

Yep. That's a new bit of hose as well. The one that was on there was very cracked, so I spent up big on the $1.40 worth of hose to replace it

[jrobie79]

go on m42club.com and look for the "mess under the intake" thread

[econti]

So.
Replaced almost every hose and shortened the route of them all.
Now it seems as if it's idling high haha. Is there a way I can manually lower the idle?
-note: I don't know what RPM it's at because my tach doesn't work

And how do I tell if a fan clutch is bad?
Once the car's hot, I can spin it by hand and it'll do a revolution before stopping with a half decent spin.
When it's cold, it gets maybe a third of a turn around.

[bmwman91]

Have you cleaned out the idle control valve? You can use TB or MAF cleaner spray. Often times, the oil vapors from the PCV system will gum up the little door in the ICV and cause it to stick.

The fan clutch sounds OK from what you describe.

[econti]

The fan clutch is the problem.
Ran it until it was warm then stuck the newspaper in. Stopped spinning straight away.

Are all clutches interchangeable? Can I use one off a M20?

[BraveUlysses]

http://bmwfans.info/parts-catalog/11521740962/

according to that, same part as M20 and M50 engines