Catchcan issues, vacuum leak? 1992 thunderbird sc


Registered User
So I have a single catchcan setup currently. It was going directly into each valve cover going over the pcv valve on passenger side and over the breather elbow on driver side, deleting the hose going from driver valve cover to the intake. I also took the small hose coming from the pcv valve took this metal piece off that was connected to the pcv valve which broke off and ran back to the intake plenum, so I ran a new rubber hose to that port on the plenum closing the system. I was told this was wrong and I need to have one of my catchcan hoses going to that port on the plenum and my other catchcan hose going over my pcv valve like I had it. And that I was supposed to have a breather hose running from driver side to air intake. So I set it up how I was told to and now I have this hose that I had taken the metal piece off of and re routed to the plenum just sitting here because my catchcan is now going into that spot. Can I plug this line, or do I need to hook it up somewhere else or put it back how it was. I start the car up now and it runs choppy and rough, before changing the catchcan it didn’t do this so I’m stuck. Any help I appreciate


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SCCoA Member
I'm not following your description above completely, but basically the PCV system is a loop...vacuum behind the throttle plate is higher than the intake tube, so clean (metered) air will be drawn from the intake tube, through the driver's valve cover, out the passengers valve cover (thru the PCV) and into the supercharger inlet (behind the throttle body)...all by the vacuum that is present behind the throttle plate. When some crankcase pressure builds at high RPM, it can escape by reverse-flowing into the intake through the crossover tube.

If you want to retain the PCV function, you have to maintain a similar vacuum loop. Usually, the catch can is meant to capture oil mist between the PCV and the supercharger inlet and the rest of the system stays the same. You can go several routes with the PCV -or- venting, but in the end you need to make sure that you don't pull UNMETERED (by the MAFS) air into the system anywhere (aka: a vacuum leak).

I think that it's likely you have a vacuum leak right now.