98 Subaru Legacy Sedan SUS idle problem

Ok now bear with me. My friend and I decided to replace the head-gaskets on this baby ourselves. We had just bought it from the original owner so the car was in mint condition with only about 140K on it. It needed the head-gasket so we thought to do it ourselves and keep the car. We manage to get it done (with a heck of a lot of trouble). However, now when we start it up, it won’t stay on for more than 5 secs on idle and then shut-down. We thought it can’t be a mechanical thing because the cars starts. If we had put a shaft in wrong, we wouldn’t be here typing this up. LOL. Anyways, we’ve been told to reset the computer by leaving the battery out and as well as manually resetting it from the computer under the driver-side dashboard. Still doesn’t help. We’ve run out of ideas and have no idea what to do now. We may think that it’s some sort of sensor problem or timing belt issue or something, but for now we are done with guessing. Anyone think they can guess what’s wrong here?

It could be a vacuum problem, a hose that was either connected wrong or left unconnected. Also could be that the Mass Air Sensor was left disconnected or it is no good.

Go back and look at everything and see it something is loose.

Are you sure the intake manifold is bolted tight, straight and with the proper gasket. Another thought, was the head gasket the correct one.

Just asking, you never know.

Did the engine run normally when you bought the car?

I’d remove the timing belt cover and make sure the camshafts are correctly timed with the crankshaft. Then I’d want to check fuel pressure. Do you have good compression?

Yeah, it was the right one. My friend is the one more mechanically inclined so I’m sure he got it right. He did most of the job, he should probably be doing this post. LOL. Concerning the manifold, it was put in properly. I will check for loose hoses and get back to yah.

It was the whole reason we bought the car. It was a babe. The only reason we thought it need a new head gasket was because the owner told us it heats up. However, it was the middle of winter and we drove it from the owner to our house (about 20 miles) and it drove great. We will look at the timing belt, fuel pressure, and compression.

Thanks for the advice. I did check the Mass Air Sensor and there was a large unattached vacuum line between the sensor and the intake. It was re-attached and it worked! Thanks for all the help. We felt stupid to not realize such a big oversight.