03 subaru legacy engine trouble

Clint Kline

Asked by Mar 28, 2016 at 06:37 PM about the 2003 Subaru Legacy 2.5 L

Question type: Maintenance & Repair

2003 subaru legacy l wagon 2.5

Misfiring, backfiring, loss of power, engine vibration, stalling, now wont move. I have po301,
302, 420, and 457 codes.

Replaced plugs, wires, fuel filter, upstream o2 sensor, and crank sensor. Im out of ideas and
money. I need to know what this issue is soon or I may just drive the thing off a cliff and never
look back. at my wits end. Please help.

2 Answers


The po302 was a miss fire on cylinder #2, P0420 SUBARU - Catalyst System Efficiency Below Threshold... Possible causes... - Three way catalyst converter Bank 1 - Exhaust tube - Intake air leaks - Fuel injectors may be faulty - Fuel injector leaks - Spark plugs may be faulty - Improper ignition timing - Engine Control Module (ECM)... Some Tech notes.... As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first.... P0457 SUBARU - EVAP System Leak Detected Fuel Cap Loose/Off... Possible causes.... - Missing fuel filler cap - Incorrect fuel filler cap used - Fuel filler cap remains open or fails to close - Foreign matter caught in fuel filler cap... EVAP control system has a very large leak such as fuel filler cap fell off Possible symptoms... - Engine Light ON (or Service Engine Soon Warning Light) - Possible a noticeable fuel odor caused by the release of fuel vapors.... P0457 Subaru Description.... This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using engine intake manifold vacuum. If pressure does not increase, the Engine Control Module (ECM) will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve under the following vacuum test condition... The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this depressurization is implemented, the EVAP canister purge volume control solenoid valve will be closed.


You need an ignition coil. $40 on eBay. Keep it simple.

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