Vacuum Canister

[greenchevy]

Ok i know that there are many threads addressing the vacuum canister behind the bumper on the passenger side but I haven't been able to find a straight answer on where or not the vacuum system on top of the engine(drivers side) ties in to the vacuum canister on the passenger bumper. When i accelerate the vent moves to the defroster. Also my cruise control doesn't work very well. I've read that this is because I have a leak in the vacuum canister system. Since the vacuum canister is a system in the vacuum system of the car. Would a leak in this system cause my jeep to have a idle problem? Since I've had the jeep (5 years) I've had an idle problem,vent problem, and cruise problem. I've replaced the vacuum harness(on top of the engine) and it helped, its not so constant but its still there. I've tested and replaced the TPS (was out of spec and couldn't adjust it. I've tested the map sensor. I've cleaned the IAC valve with no change. I haven't found an air leak around the throttle body,exhaust manifold, intake manifold. I'm lost at this point but the only thing i can think of is the leak in the vacuum canister system is causing my idle problem. I've read on many threads over the internet about people saying they have no ill effect on the jeep(Whether they have them or removed,ripped them off). But to my understanding it ties in to the vacuum system so if there was a leak it would cause problems with the engine. Thanks to all of you that read my very long ramble and understand what my question is. If anyone can help me with this that would ease my confusion.

[4.3LXJ]

Yes, all the vacuum for the Jeep comes from the intake manifold. You don't have to have the reservoir, but if you don't every vacuum operated thing will quit when you put the pedal to the metal. It evens things out by storing vacuum. Also make sure your check valve (little disk in the line) is working.

[greenchevy]

So A vacuum canister leak could cause my idle problem?

[4.3LXJ]

You haven't explained what that problem is. Is it rough, does it lope?

[greenchevy]

I have a high idle. The tach kneedle moves up and down.

[BlueXJ]

Probably not a high idle. Check the IAC to see that it is connected tightly at the electrical connection. You may want to remove and clean it as they get carbon buildup and move poorly when that happens. Be very careful not to harm the pintle that sticks out, they are easily bent.
See if that solves your high idle problem.

[greenchevy]

I've cleaned it multiple times with no change. Also replaced it with no change. When I start it the idles goes up then it goes down toward 1000 rpm then it starts to go back up then down its keeps doing that.

[4.3LXJ]

You might try spraying something like WD40 around the throttle body and see if that affects RPMs. This would indicate a leak. Also look down the throttle body and make sure the butterfly makes a good seal. There should be no gap there. Might try some WD40 in there too to see what happens. If RPMs change, you might need to remove it and clean it and reposition the butterfly

[greenchevy]

That is one of the first things I did and found no leaks.

[4.3LXJ]

It might be time to replace that IAC then. It sounds like it is trying to work, but not cutting it. And if it is clean, there is nothing more you can do for it.

[greenchevy]

I'll replace the IAC valve again and post results. I've read that it could be my egr what are the test procedures?

[4.3LXJ]

That is a good point. They get carbon in them and don't seat. Might check and clean it first.

[Mudderoy]

Did you check the TPS?

[greenchevy]

Yes replaced tips. It was out of spec. But don't notice a did fence. New one is in spec

[ParadiseXJ]

So A vacuum canister leak could cause my idle problem?

You DO have a vacuum system leak if your HVAC cuts to defrost when you accelerate. I don't see anywhere that you have found or fixed any such leak.

The source vacuum from the manifold only brings vacuum to the HVAC system, the purge system and the Cruise Control (if equipped). I doubt(my opinion) if a tiny leak in one of the small pass. side hoses would cause a running or driveability problem. But it will cause the blend doors to default to defrost mode. A cracked hose, a loose connection, a tiny wear or corroded spot, especially under the battery tray where the vac lines dive down to the canister are all likely suspects.

It's fairly easy to find a vac leak on a 4.0. Blow a little smoke (and when I say smoke, I don't mean from a smoke machine, invest in a $1 cigar) into each hose...see where it comes out = leak. REPLACE any questionable lines. That'll fix your HVAC leak. If that fixes your idle problem...great, if not check the lines to your EGR solenoid.

For HVAC system there are two small tubes coming out of the firewall...one tan or pink, and one black. The tan/pink line goes to the heater control valve (if equipped). Follow the black one to the vacuum canister and/or to the cruise control...I have never seen a leaking canister unless the bumper has been hit and the can is cracked - unlikely. I relocated my canister into the engine bay and eliminated about 3 ft. of possible leaking hose.

Then start checking the lines from your valve cover. Tight grommets, elbows, fuel pressure regulator, CCV, etc. You can use the smoke system here too, but usually a visual check of the vacuum line harness near the front of the VC and the bends, elbows and fittings will do the trick. All the vacuum lines, except the moulded hard lines and pre formed harness lines are dirt cheap and well worth just buying bulk hose and a handful of fittings can be had for less than ten bucks. I even have some plastic sprinkler hose for vac lines on my MJ.

The pre formed lines, including the CCV and associated grommets can be found at NAPA in two halves for around 40 bucks. The grommets may look OK on the outside but take a look at these pics:

Here's my OLD CCV grommet, looks pretty good, eh?

http://i168.photobucket.com/albums/u196/chasdwitt/ALL%20JEEP/076.jpg

Here's what it looked like on the inside:

http://i168.photobucket.com/albums/u196/chasdwitt/ALL%20JEEP/075.jpg

...and now the NEW CCV grommet on the inside:

http://i168.photobucket.com/albums/u196/chasdwitt/ALL%20JEEP/077.jpg

So, the thing has deteriorated and swollen up from heat, oil and age to block off the "metered orofice" to almost zero. The metered orfice is supposed to be 2.6mm. Here is a picture of what 2.5mm looks like, I swiped this from the doctors office when I saw that it said 2.5mm as I was waiting for the doc. I don't condone swiping things from the doctor but they have thousands of them...and the visit cost me 120.00 anyway.

http://i168.photobucket.com/albums/u196/chasdwitt/ALL%20JEEP/080.jpg

Yep, 2.5mm for the earscope will tell you if you're getting enough vacuum from your CCV. Also, blow out all your vac lines with compressed air just to get the gunk out of them, your engine will thank you.

[greenchevy]

Checked egr and it passed. Don't know what to test next?