Vacuum manifold issues.

[jaystrawn135]

I have a 1988 jeep comanche 4.0 6i, 2wd.

The truck runs good as long as you have 2 of the vacuum manifold lines unhooked, If not it acts like it choking.

Would that be the manifold lines themselves or would it possibly be a sensor or intake issue?

I had someone tell me those lines are prone to flaking apart on the inside and clogging up. I'm ordering a new vacuum manifold either way (they're just $40 so screw it.) just wanted to see if there is something else I should be looking into as well.

[Pete M]

which ones are unhooked?  where do they lead?  are you introducing a vacuum leak to make it run right? (or are you plugging the open holes in the manifold with your fingers?)

[jaystrawn135]

8 minutes ago, Pete M said:

which ones are unhooked?  where do they lead?  are you introducing a vacuum leak to make it run right? (are you plugging the open holes in the manifold with your fingers?)

I'll have to try to figure that out tomorrow. I guess I got it with them disconnected. I was up under the hood and my dingus of a brother-in-law decided to "help" and started shoving his hands all up on $#!&, then realized they were unhooked and thought he knocked them off. So he reconnected them and it started running like $#!&, it runs better when I disconnect the small line in the middle and the line on the bottom that runs back to the breather. And plugging the holes with my finger is about the same as putting the hoses back on, it starts running like crud again.

[jaystrawn135]

I changed out the whole vacuum harness and pcv line and the problem persisted. Ended up hearing a rattle in the cats, I pulled of the muffler and there was a peice of my cat that had broke off and was sideways in the outlet to the cats. Busted that out and problem solved 👌 🤣  lmao I never would've guessed that as the issue 😂 

[Pete M]

ahhh, that's a lot of backpressure messing with the system.    but glad you figured it out!   

[pizzaman09]

54 minutes ago, jaystrawn135 said:

I changed out the whole vacuum harness and pcv line and the problem persisted. Ended up hearing a rattle in the cats, I pulled of the muffler and there was a peice of my cat that had broke off and was sideways in the outlet to the cats. Busted that out and problem solved 👌 🤣  lmao I never would've guessed that as the issue 😂 

I had that happen to my Oldsmobile, GM 3800 series II.  I figured it out when I looked under the car and saw the cat glowing.

[jaystrawn135]

36 minutes ago, Pete M said:

ahhh, that's a lot of backpressure messing with the system.    but glad you figured it out!   

Yea, I figure the back pressure might explain why my air filter would get oil blown back into it 🤣. I read somewhere that oil on the filter was a normal issue with these, but it would actually get a lil wet if I ran it for too long. Drove it for over an hour earlier with a new air filter and not a drop to be seen.