Car violently bucks and jerks when I take my foot of gas pedal to slow down and then apply subtle pressure to accelerate again. Impossible to drive in stop-&-go traffic. 1992 Legacy, manual. Has new fuel pump & filter. Intermittent problem, becoming more prevalent. Has been in shop numerous times, various parts have been replaced. Had broken wire connection in harness under back seat, fixed. Mechanic clueless.

SOURCE: Car won't start and floods

Sir,

You can check fuel pressure and Low fuel pressure may cause a lean trim mode so the PCM will compensate by adding more fuel to the fuel injection system to compensate.

Also, remove the vacuum line at the fuel pressure regulator and check for raw fuel indicating a ruptured diaphragm. A flaky fuel pressure regulator may cause longer than normal starting but the fuel pressure check will test it. Check at fuel pump prime, at idle and with the vacuum line at the fuel pressure regulator on and off.

Thanks
Good luck


"Don't forget to rate the solution"

SOURCE: Car won't start and floods

Locate your vehicle's computer connector (ALDL), most are on the lower driver's side. In some vehicles you might need to look around a little, on the passenger's side, and around the center console under a plastic cover. For more information, check your owner's manual. This device gathers information that was stored in your carsECM. This information ortrouble code can inform you the system or sensor that is malfunctioning. Look up the code in our diagnostic trouble code chart. After repairs have been made use the code scanner to clear trouble codes and recheck system. B. Testing Fuel Pressure. Test for proper fuel pressure with a fuel pressure gauge. Connect the gauge to the test port on the fuel rail. Fuel pressure reading's very depending on the system your in our vehicle, but most throttle body injection cars (TBI) are between 13 psi and 17 psi. and most (DPI) direct port injection systems are between 40 psi and 55 psi. To find out your vehicle system fuel pressure consult arepair manual. If little fuel pressure is present the fuel pump needs to be replaced.

C. Test for Weak Ignition Spark. A weak ignition system can be a sign of a failing ignition component. Remove spark plug wire and insert an extra spark plug into end of wire, attach spark plug to engine ground then crank engine. You should observe blue spark between spark plug gap. If a yellow spark is observed, your ignition coil is weak and needs to be replaced. If your spark is not consistent you may need a ignition module.

D. Inspect the Main ECM Relay. If the ECM relay fails it will shut down the engine management system. This relay carries high amperage and is prone to failure. To test install new relay then test drive to recheck symptoms.

E. Testing the Ignition Switch. This test requires a electronic test light. When vehicle dies test the power side (+) of your ignition coil with the key on, the test light should illuminate. If your test light is not lighting suspect your ignition switch or ignition relay. To trouble shoot this condition you will needwiring schematic for your car.

SOURCE: How do you replace the fuel pump in 1992 2wd Subaru Legacy Wagon

1. Relieve the fuel system pressure.
2. Disconnect the negative battery cable.
3. Remove the rear exhaust pipe and muffler assembly.
4. On All Wheel Drive (AWD) vehicles, remove the rear differential assembly and the rear crossmember. You do not have AWD so this step is not for you
   
5. Remove the fuel filler cap and drain the fuel into a suitable container.
6. Remove the fuel filler pipe protector.
7. Raise and support the vehicle safely on jackstands.
8. Remove the fuel filler, air vent and delivery hoses.
9. On AWD vehicles, disconnect the air breather hoses and evaporation hose from the pipes.
10. Support the fuel tank with a floor jack or equivalent lifting device.
11. Loosen the attaching bolts and lower the fuel tank slightly.
12. Disconnect the fuel pump harness
    

SOURCE: Subaru stalls while driving, and idling

check the cam and crank position sensor making sure that there is no metallic deris

SOURCE: Check engine light and intermittent bucking

You might get lucky here. Go out and open the hood and start the engine when it's dark. See if you can see sparks jumping around the spark plug wires. That will tell you for sure. Otherwise, my first choice would be to put on new plug wires of the highest quality you can find. I've seen this type of problem before, and it can be made worse if the boots on the wires are not clean or too much grease was used at the factory. The solution was to clean everything and replace the wires and spark plugs because carbon tracks have been created that can't be easily (if at all) cleaned from the spark plug insulators. The coil towers will probably be okay if you clean them well.