What the hell is...?

[TNR]

What the hell is this? Anyone know??
Here's the rundown, it starts in the first pic.. looks like a vac line.
The goes across the engine bay, thru the same foam retainer as the wiper wash lines (if they were there anyway) and to a 3 way junction (2nd pic)
the 3rd pic is a blurry (sorry) pic of the connector upclose.
I can't seem to find any logical place it's supposed to be hooked up.

 

[Darrman]

Ok, I had to go out and check mine, I knew I recognized that line. I dont know what it does, but I can tell you where it hooks up. on the vacuum tree on the side of the intake, there are two ports that directly face the front of the car. In the pic of yours, there is something already plugged in, its the little elbow plug, thats where the loose one is supposed to be. I dont know why that elbow is in its place, but thats the way mine is setup, and it all works.
I recognized it because I have already broke both sides of the line, damn brittle little thing, had to patch with rubber tubing.

 

[sparky2263]

Checkvalve for the HVAC and cruise control. One line should be manifold vacuum, one should go to the vacuum reservoir and the other should head to the firewall.

 

[TNR]

I though it might be something for the climate control. Possibly, the prior owner disconnected it when the A/C compressor went out.. Would that make sense for someone to do that so the a/c wouldn't turn on? If so, would this one affect the engines idle at all?

 

[TNR]

Ok, I had to go out and check mine, I knew I recognized that line. I dont know what it does, but I can tell you where it hooks up. on the vacuum tree on the side of the intake, there are two ports that directly face the front of the car. In the pic of yours, there is something already plugged in, its the little elbow plug, thats where the loose one is supposed to be. I dont know why that elbow is in its place, but thats the way mine is setup, and it all works.
I recognized it because I have already broke both sides of the line, damn brittle little thing, had to patch with rubber tubing.

In the second pic where I put the arrow, that is all one tube it goes from there to the unplugged end all the way across the engine bay..

So Im still not quite clear about where the end that is currently loose is supposed to plug in.. any way you can take a pic to show me what you mean? (sorry, stuck on stupid here... )
thanks!

 

[Darrman]

In the first pic you have the loose end (unplugged), near it is the vacuum tree, which is mounted on the side of the big intake plenum, you have all your other vacuum hooked to it, brake booster etc.
If you stand at the front of the truck and look at the tree, there will be two of the vacuum ports (hookups) that face you, the one you want is the inside one (closest to the intake). There appears to be something hooked up there already, you will need to find out what it is first.
I am at work now, but I will try to get a pic later, if this doesnt help.

 

[TNR]

In the first pic you have the loose end (unplugged), near it is the vacuum tree, which is mounted on the side of the big intake plenum, you have all your other vacuum hooked to it, brake booster etc.
If you stand at the front of the truck and look at the tree, there will be two of the vacuum ports (hookups) that face you, the one you want is the inside one (closest to the intake). There appears to be something hooked up there already, you will need to find out what it is first.
I am at work now, but I will try to get a pic later, if this doesnt help.

Right, thats my question
I see the tree in question. But it appears to all be plugged in, there are two on the firewall facing side of that tree, but they are populated with smooth plastic covers.

 

[410Fortune]

Wow it looks like your previous owner might have been messing with this stuff for sure.

Okay off the tree on your 91 5 speed you should have vacuum feeds to:
cruise control canister (looks like I see this one)
brake booster (looks to be there)
fuel pressure regualtor (check this one)
EGR valve (check this one)
Vacuum canister/airbox/into the cab for HVAC controls (off the T pictured in photo #2)
BAP or MAP sensor (the 91 4.0L had a MAP sensor, it looks to be missing from your truck, this would explain the unplugged vacuum line)

the MAP sensor would be mounted on the firewall just to the right of the vacuum canister if I remember right. Is there an electrical connection anywhere you can see for this sucker?

Now regardless, this line should be hooked up the manifold vaccum, it appears to be the feed for the T pictured in #2, not sure what the previous owner did but yo need to make sure all this stuff is hooke dup and has vacuum. Then you need to check the plastic lines for leaks. Then you need to remove one of the caps on your tree and hook this line back up, then check it for leaks.

Dont leave it open to the atmosphere. It might not be causing any issues with your 4.0L running (like you are having inthe other thread) but chances are this unplugged line needs to be plugged in.

 

[TNR]

Wow it looks like your previous owner might have been messing with this stuff for sure.

Okay off the tree on your 91 5 speed you should have vacuum feeds to:
cruise control canister (looks like I see this one)
brake booster (looks to be there)
fuel pressure regualtor (check this one)
EGR valve (check this one)
Vacuum canister/airbox/into the cab for HVAC controls (off the T pictured in photo #2)
BAP or MAP sensor (the 91 4.0L had a MAP sensor, it looks to be missing from your truck, this would explain the unplugged vacuum line)

the MAP sensor would be mounted on the firewall just to the right of the vacuum canister if I remember right. Is there an electrical connection anywhere you can see for this sucker?

Now regardless, this line should be hooked up the manifold vaccum, it appears to be the feed for the T pictured in #2, not sure what the previous owner did but yo need to make sure all this stuff is hooke dup and has vacuum. Then you need to check the plastic lines for leaks. Then you need to remove one of the caps on your tree and hook this line back up, then check it for leaks.

Dont leave it open to the atmosphere. It might not be causing any issues with your 4.0L running (like you are having inthe other thread) but chances are this unplugged line needs to be plugged in.

If I unhook a vac line, and put my finger up to it, I should actually FEEL the vac right?

 

[410Fortune]

Sorda

If you dont then it should be hooked up to vacuum.

You see this sucker looks like the feed line that is supossed to take manifold vacuum over to the T, which then feeds the canister and the airbox sensor.

 

[Tony H]

It is for the climate control. Plug it in to the Little Manifold coming off the top of the Upper Intake manifold.
Follow the hose from your Pcv valve. I just had that hose off the other day when I had the Intake off.

 

[TNR]

I see..

That would explain it. I took off one of the caps on a nipple sticking out of the manifold and plugged it in, it made no difference in the idle, however, Im now questioning the accuracy of my tach. This morning, doing 70 on the highway it was at 3600 rpm. The other day when it was warmer out, the same speed resulted in a 2900 rpm reading.

Just a difference in tempature. I wish I still had that reader my friend loaned me. Any good suggestions on semi-inexpensive things I can plug into the truck to get the exact readings again? Somethings up, the engine is feeling "rougher" during idle and accel now too...

 

[TNR]

Sorda

If you dont then it should be hooked up to vacuum.

You see this sucker looks like the feed line that is supossed to take manifold vacuum over to the T, which then feeds the canister and the airbox sensor.

410, Where is the map sensor supposed to be located?

 

[410Fortune]

the MAP sensor would be mounted on the firewall just to the right of the vacuum canister if I remember right. Is there an electrical connection anywhere you can see for this sucker?

 

[TNR]

the MAP sensor would be mounted on the firewall just to the right of the vacuum canister if I remember right. Is there an electrical connection anywhere you can see for this sucker?

Not that I see.. I could be wrong tho.. Im not totally knowlegable about these sensors, what they look like, and related connectors.. anyone have a pic for me?
BTW on that Vac line.. I decided to stop being stupid. I started messing with vac lines WHILE I had the truck running. When I unplugged that rouge line with the truck running, I heard the hiss of the vac, and the engine started stumbling, even with my manual control of the "idle"

Funny thing is.. when this line was disconnected and hanging there before It caught my attention, I heard/felt no such vaccum from it. now I do after its been plugged in for a few days... go figure.

 

[sparky2263]

This help any? The MAP sensor is called a BARO sensor here.

 

[TNR]

This help any? The MAP sensor is called a BARO sensor here.

Sparky, it looks like it REALLY could be.. but I can't read the text, do you have that in a larger version?

 

[Mbrooks420]

Looks like it is 5 over from the right on the top line of text.

 

[savagefan]

There will be no vac line to the bap (baro) sensor. Mine just quit, left me stranded.

 

[sparky2263]

Correct. His would be Baro only, no vacuum line. The 91 doesn't hook a vacuum line to the Baro (although they are the same sensor) as it gets its fuel calculations from the MAF.

I'm wondering if the rougher idle and accel. is due to a dirty/contaminated MAF sensor.