my head gaskets were leaking so I took them off and got a good deal on a set of heads so I pulled the cam and stuff off the old heads put them in the new heads put it all back together and now when I start it it goes RevVvvvvvvv up to about 3500 RPM then comes back down and then really really rough idle and the whole motor shakes really wildly then it will die unless I give it some gas then it will spike back up and repeat the process I can't really keep it at a idle and if I can manage to do that it's sooo horrible... so what should I start with? or what did I do wrong.... I didn't adjust the valves.... would that cause this prob?

 

Thanks so much

 

Jonathon

 

PS it's a 1990 Legacy 5 spd Manual

did you put the 1" dia hose from the main plastic intake to the Idle Air control motor back on? It's under the plastic intake and goes to the passenger side of the throttle body.

+1 to a vaccum line somewhere... mostlikely the one under the filterbox like 91 Loyale said.

Hummm I'm not sure where the Idle Air control motor is.... what does it look like? and as far as I know I got everything hooked back up I don't see any loose hoses or anything and I marked everything with a paint pen to make sure everything went back together the same.... is this thing under the intake manifold?

ok I think I found it... looked in the Haynes manual so on the pass side right back from the coil and down there is a hose that goes into something and that hose goes to the air intake line.... so is that the right one? if so yes it's connected

The 1" line mentioned above has gotten a lot of people over the years, so it's what everyone suspects first. I don't think your engine is built quite that way in any case, but if that line is disconnected on a 2.5 engine, the engine can breathe through the idle control valve without the flow being counted by the air flow meter, this throws off the fuel mixture, and will prevent idle, but the car will normally run fair at about 2500 rpm or higher. The symptoms you describe are essentially the same, so I'm guessing you have a big vacuum leak after the throttle plate, or a disconnected hose that connects to the intake manifold. The hoses between the air flow sensor and the throttle body must be leak tight as well

The 1" line mentioned above has gotten a lot of people over the years, so it's what everyone suspects first. I don't think your engine is built quite that way in any case, but if that line is disconnected on a 2.5 engine, the engine can breathe through the idle control valve without the flow being counted by the air flow meter, this throws off the fuel mixture, and will prevent idle, but the car will normally run fair at about 2500 rpm or higher. The symptoms you describe are essentially the same, so I'm guessing you have a big vacuum leak after the throttle plate, or a disconnected hose that connects to the intake manifold. The hoses between the air flow sensor and the throttle body must be leak tight as well

 

 

Thanks everyone, it turned out to be a leaking air between the intake manifold and the heads so took the intake off again and put silicone on and now it's good..... except now I have this problem...

 

http://www.ultimatesubaru.org/forum/showthread.php?p=601145#post601145