So my 98 subaru impreza acts rather funny for the first 5-10 minutes after start up. Basically what happens is I turn the ignition and it takes longer than usual to start up and when it does the car acts like its running on fumes. When I’m idling the car shakes like its struggling to get fuel in the engine and when I drive it it jerks along for the first 10 minutes or so when I have to accelerate. Usually after about 10 minutes of driving the problem goes away, but since I primarily drive it to work abut 15 minutes away, its like the majority of my commute. The problem usually happens more when i let the gas get below 3/4 of a tank so I try to keep it topped off.
Any help for this problem would be greatly appreciated.
The first thing that should be done is have the fuel pressure tested to check if the fuel pump is weak. If the fuel pressure is at or below the minimum spec it can cause this problem. When the engine is started cold the demand for fuel is at the greatest. If the fuel pump isn’t capable of delivering the proper pressure and volume of fuel to the cold engine, the engine will run rough and lack power. Then as the engine warms up and the demand for fuel decreases the engine runs normally.
A quick thing to test would be to loosen the gas cap, and then try to start it. If it starts fine, your tank isn’t venting properly (which leads to Tester’s weak fuel pump, only the fuel pump isn’t really weak, but not strong enough to overcome the vacuum).