[canuckrookie]

Hello...Newbie here.

Just bought a 1997 Mustang Cobra with a brand new rebuilt 4.6L DOHC engine in it. Drove fine for first few days and then it started to stumble really bad on idle and even stall out.

I have read all of the posts related to stumbling on these engines at idle and have chaecked the IAC etc. for problems.

What I found was that the car had a CAI on it and the PCV hose from the passenger side valve cover was sucking air big time creating vacuum at idle.

Now, I'm no engine genius but PCV is supposed to push air from the crankcase out through the PCV and back into intake manifold not suck air into the pcv and into the engine.

I can stick my finger on the end of the hose and the vacuum pressure will keep my finger stuck on the hose.

I am completely stumped on this and I have ended up taking hte car into a Ford Performance dealer but does anybody know what this could be caused from and why all of a sudden this would happen?

The car did have a supercharger on it before which was removed when i bought it...Is there a reverse PCV that you use with superchargers that I don't know about???

Any help appreciated.

[tripleblack]

Here is how the PCV should work, if its plumbed right:

The system relies on the fact that, while the engine is running, the intake manifold's air pressure is always less than crankcase air pressure. The lower pressure of the intake manifold draws air towards it, pulling air from the breather through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.

There will be vacuum present on the inake side, vs the plumbing from the crankcase. The PCV valve is a one-way valve (though it can get stuck either closed or open).