Vaccum

I'M NEW SO BEAR WITH ME. 1st : On the front of the engine drivers side there is a vaccum tree with several ports. One is not connected to anything but it appears that it had been. My '90 XJ idles fast but if I plug this port the idle slows a bunch. The EGR hose is not connected to any thing but the hose is not near long enough to reach. No other visible hoses around.
I bought this XJ a while back and know nothing about it's history. What should plug on the port?
4.0 inline 6

I also have a '90 XJ. The EGR valve vacuum line goes through an electric selenoid located on the body on the right side of the air cleaner box before connecting to the intake manifold via that "tree".

Sounds like you have a vacuum leak somewhere.

The "tree" of vacuum hoses is just an easy way to disconnect them all at once and can be bypassed. On mine one of the larger ones has nothing on it as well. Im in the process of removing all that stuff, except the EGR hoses when I put in my new Intake. Im finding that some of the old lines have cracks in them and need replacing anyway.

Thanks, At Least I Now Know Something About It. I Connected My Egr Hose To The Air Cleaner Cause That's The Only Thing Close Enough. It Has A Hose Comming Out Of The Air Cleaner Through The Solenoid. I'll Check Futher.

From the EGR the vacuum line goes through a vacuum transducer (right next to the EGR) then through the electric selonoid, then through that vacumm tree, then into the port on the intake manifold.

That front port on the manifold has 3 Vacumm hoses:
1. EGR selonoid, through that connection tree.
2. Air cleaner box, through that connection tree.
3. Fuel rail regulator, through that connection tree.

The Air Box has 4 hoses: (aside from Throttle body intake)
1. To Intake manifold, small hose (mentioned above)
2. To Thermal control air cleaner inlet valve, small hose
3. A Large hose coming from valve cover through that Tree.
4. To charcoal canister, large hose

The Valve cover has 2 CCV hoses:
1. Clean air in form the Air Box, large (as mentioned above)
2. The crankase air out to intake manifold, has its own fitting.

Note that there are also 2 other hoses coming from the intake manifold:
1. To the brake power booster, large hose
2. Another that goes to the other vacumm accessories like axle disco, ...

does anyone have a diagram of the vaccum system? my '94's 4.0L idles relaly roughly. I found one crack in the hose leading to the vaccum reseviore. So i cut the hose above the crack and relocated the can next to the batery. Where are some common problem areas? thanks you and sorry for jacking this thread

They have the vacuum diagrams in the Haynes manuals. Its like $18 at Autozone or any parts store..

Anything that connects to the intake manifold could cause you idleing problems.

So this vaccum canister has to with the idel? Because mine idels really high at like 1500 rpms, my canister right now doesnt exist, i need to get a new one. What does this canister do anyway???


Thanks

AJ

The vacuum cannister stores vacuum (obviously!) which is used for the cruise control actuator (if you have it) and for the heater plenum valve controls.

Anything that is vacuum-operated or has/is a vacuum line can cause an idle problem. If you want to check for a vacuum leak, you take a can of carburettor cleaner, let the engine idle, and spray a fog around all the lines you can find. You will see the cloud get drawn into the system and the idle will "race" a little more when it gets the cleaner.

Along with all the lines (especially the Nylon ones,) keep an eye on the manifold sealing surface. The I6 has a long sealing surface, and the bolts have to hold down aluminum and steel. Aluminum expands twice as much as steel when heated, and that causes the bolts to gradually work loose. I retorque all mine about once a year (three active XJs) for good measure.

Keep an eye on the MAP line at the throttle body - I've noticed that they can come loose over time as well. It's retained with a barbed nipple in a blind hole (the upper, I think) that can be lightly siliconed and it will stay put.

The underhood emissions tag should have a full engine vacuum diagram on it - if you can't find it, let me know and I'll dig around for it. Give me a couple days.

As far as the vacuum cannister, they tend to crack when they get older, and cause a vacuum leak as well. Probably should be replaced if it's over ten years old and starting to leak.

I'm working on a good idea for making one out of metal so I don't have to worry about cracking later...

5-90

thanks ill try some of ths stuff