1993 Subaru Impreza back fire

1993 SUBARU IMPREZA
220,000 MILES • 4 CYL • FWD • MANUAL
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WESHTA538
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hi
1993 subaru impreza has been backfirng hard.
today changed the spark plugs and the leads but still the same problem!!!!
it does it up until i get to 3000revs and then drives normally its lags and then picks up, cough cough splutter drives fine
Jan 11, 2010 at 4:17 AM
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RASMATAZ
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Could be ignition timing, rich/lean fuel mixture, spark plugs wrong heat range. also the following below

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Jan 11, 2010 at 10:01 AM
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WESHTA538
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got it in the dark last night the two right spark plugs are sparking very badly,
Jan 11, 2010 at 5:06 PM
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RASMATAZ
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Its crossfiring it will cause the engine to backfire firing at the wrong time
Jan 11, 2010 at 5:57 PM
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WESHTA538
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how do i fix that??????//
Jan 12, 2010 at 2:43 AM
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RASMATAZ
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Replace the plug wires its leaking
Jan 12, 2010 at 12:32 PM