What would cause a car to immediatly shut down after starting?

I've been working on this 99 Subaru Legacy Outback. For the last couple of weeks it's had a check engine light on it. I checked the code and it told me that the #4 cylinder is misfiring. First I put in some fuel cleaner, that didn't do any good. So the next thing I tried is replace the spark plugs and cables. As soon as I did this the car started to shut down immediately after starting unless I keep feeding it gas. So what could cause this? What can I check?

2011-07-17T18:28:26Z

@Rich Sandstorm:

I'll check again but I didn't see any loose wires. I'll also get the codes checked. To answer the other two questions it seems to be running smoothly when gas is a applied but when it stalls out it shakes quite violently.

2011-07-17T19:02:53Z

Checked the codes again. The P0304(misfire in cylinder 4 is still there) and there is now a new one P0440(the guys at autozone said it was something to do with exhaust and emmissions).

Anonymous2011-07-17T18:22:54Z

Favorite Answer

Well assuming you changed the plugs and wires one at a time and Gapped them correctly, and didn't drop them and they are the correct ones! I would start by looking to see if you knocked a wire off of a sensor! See if there are any codes did you clear the missfire code? Does it run smooth if your foot is on the gas is it shaking?Is it a stall or is it like someone shuts the key off?

bandit_602011-07-18T01:22:14Z

check the fuel pump regulator. it might not be putting enough gas into the injectors to keep it idling or 1 of the injectors is dirty. try some complete fuel system cleaner in the tank.