Well I know it's on the same vacuum "circuit" as the PCV. Whenever I have my oil cap on the damn thing won't even muster up a idle. Take it off, vroooom!

I found the cause of this "odd" behavier purely by accident. You can just hold, or block the hole in the valve cover, and it starts going rough, and the idle increases and gets erratic. Uncover it or unplug it? calms down, runs good. I thought my PCV valve was bad so i checked that, looked fine, but just in case I got another. Still does it. I mystified my three brothers when I showed them this, they didnt believe me until I showed them, lmao.

Anyway, I traced the vacuum lines (theres 2) and one goes to the charcoal canister, and branches off. The other goes to the throttlebody. It is now my opinion I have a vaccum plug up, or not enough. Maybe one of those hoses is stopped up, dunno. I have always heard those canisters get stopped up and affect idle, just never been through it? Should I check my vacuum? Anybody ever heard of this?

Wow, weird. Hey, try this. Pull the PCV out of the valve cover, but put your oil cap on. Start the car, see how it runs. If it runs good, put your finger over the PCV valve.

That's actually what I tried second, (first was the air filter's) and the oil cap off works better. So yes, it does it with the PCV valve unplugged/plugged as well.

Ok I searched my whole vacuum line system, (shew!) and other than slightly cracked (but usable) canister lines, I found one broken off vaccuum line, what does this do? (see pic) A rotten hose broke off it's where a hose from the firewall connects to the branch at the back of the plenum? what does this do? does it go to the computer? could it cause my woes? lmao.

The part you've indicated by a "?" is a valve that only allows airflow one direction. I broke mine while fixing another vacuum leak. I'm not sure if that's the part that's broken, but I had to go get one at the dealer (~$5) cause kragen didn't have it. But a vacuum leak from that area will definently cause problems.

Pic Time:

This is the hose drawn in the left of that last drawing, see the short, rotten hose on the end? I think it connects to...........

This..... To make a "Y" shape together with the Plenum output. The upper/smaller hose on this is slightly cracked, but it's on good. Anyway to test this valve?

And just a shot of the CLEAN new engine bay, the pic doesn't do it justice!

Anybody know what the purpose is of the vac circuit in the above pics is?

That tubbed "T" damn, I know on my wifes corisica it was bad and caused all sorts of funny things. Went to autozone, me and her couldn't find it, but all be damn if our 2.5yo found it . Put it on and it fixed idle, hissing, acceleration, heater problem. I suggest getting a new one, it was like 3 bux. Then get new hoses, or whatever else to fix any vacume lines that MIGHT even look bad.

BTW, yes that connects to that, get a new "t", "y" thingie, and put that on it. That is most deff a problem!!!!

Thanks! great info man.


I'll go and get one today, where did the little one find it? (can't ask you) lol.

It was in a red box, with all the other vacume fixit stuff. Our store it was way down low as to where she could grab it.

Awww, from the mouth, er hands of babes. LoL.

Yet, me and the wife were like, wheres it at, shes playing with stuff, pulls one out, and we went to put it back on the shelf and were like HUH, OMG, shes found it. Atleast we didn't have to listen to her complain when we normally put the stuff back on the shelf, she thought she was getting something. We even let her play with it on the way home. Get home, she wanted to take it inside, "we said, leave it here for next time", "ok", hehe then went out later and put it on the car. She never missed it, HA.

I belive those lines go to the vacum ball, and a two other things I can't rember off the top of my head. If I remember corectly one is the heater diverter vale and on my '92 3.1L one goes off to the map sensor. At any rate it's the vacum leak that is causing the problem.