Vaccum Leak

[tacamo]

PCV Valve port sucking
I have a 1997 Expedition, 4.6L Triton, 40k miles on rebuilt engine 2 years ago.
Experiencing a surging, rough idle, lack of power up hills, and poor automatic shifting. The Check Engine light is NOT on. Everything else appears normal. While checking for vacuum leaks, I found the PCV Valve (PCV Valve 2090) on the starboard valve cover has two ports, the lower larger one going to the intake manifold, and a smaller one above it un-connected. The upper port is sucking like there is no tomorrow. Thinking the cap might have come off some how, I capped it, but that causes the engine to stall. I replaced the valve, no change, same problem.

Any help as to why this smaller port would be sucking wide open would be much appreciated.

Thanks, Thomas

[tacamo]

Has anyone ever heard of this? This seems like it is a pretty good indication of something wrong, and should be able to point directly to a defect part.

Any Help Please.

[TBIRD430]

U may need to cap the OTHER END of the vaccum line... I bet it goes to the intake manifold.

[tacamo]

Are you saying I should cap at the end of the big line going to the intake manifold? I disconnected the line at the back of the intake manifold where the big line goes and it died instantly. If I also cap the manifold, wouldn't that be eliminating the whole reason for the PCV valve and the venting process?

It was working as advertised for years, and then the upper port on the PCV Valve started sucking, which is the new symptom. Something is causing the valve to suck through the upper port, because it wasn't doing that before.

ANy other suggestions?

[TBIRD430]

I was suggesting u cap it to get/keep the engine running. I have a '99 Exped. so mine only has a SINGLE large vacuum hose, which also runs to the back of my intake manifold. I don't know if someone installed an incorrect PCV valve on urs or not. Furthermore, if that is the correct PCV valve, with dual vacuum ports, I don't know where that 2nd smaller port goes. Someone else will need to chime in on this one I guess, maybe someone who has a 1997 and could look at their PCV valve/system....

Sorry.

[tacamo]

I think it may be the wrong PCV, however, I bought the correct one called out in the Checkers Computer (Fram 398) which was a single port item. When I installed it, the truck stalled. I took it back and got the same PCV that I previously had (Fram 2090) and now I have the same problem, no fix. If I cap the smaller port, it stalls.

Thanks for the help. I was hoping for more replies, as this one has got me guessing. I just can't swallow the Ford Diagnostic price of $165.

Thanks.

[TBIRD430]

Well, a PCV valve ALONE will not cause an engine to stall. I would install the new single PCV valve and go to ur local Ford dealership and get a NEW PCV tube (which runs from the rear intake manifold to the PCV valve). There has to be 1 or MORE leaks in the tube u have now....

I look forward to ur reply....

[jonmark1985]

Make sure to keep you PCV system working. Not running one can ruin your rear seal or even blow your dipstick tube.

Some after market PCV valves have two ports to replace a single port valve. They almost always include a plastic cap that you insert into the extra port if it is not needed. Personally I would get a Motorcraft valve and throw the Fram valve in the trash.

For some reason your engine is relying on the vacuum leak to stay running. I would consider pulling the idle air control valve and cleaning it. They are very prone to plugging up on late model Fords. If this is the case then IACV could be stuck shut and the engine will be searching for another source for the air required for idle. You could verify this by leaving the extra port on the PCV valve uncapped, having a helper start the engine and lightly throttle the engine. Then cap the port. Remember to keep the throttle slightly open. If the engine dies even with the throttle opened the IACV is not at fault.

Please keep us in touch and let us know what you find!