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1997 Subaru Impreza Outback Question: Starts and runs well. No evident loss of power. Stumbles at idle. 5 speed manual

 

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Tom M, 2.2L 4 Cylinder, San Diego, CA, September 11, 2013, 18:18
 Rookie

Engine returns to idle normally (i.e 750rpm) but after about 15-20 seconds, idle drops radically almost to a stall. Sometimes returns OBD codes P301, P302, P303, and P304 for engine misfire for all 4 cylinders.

Replaced MAF sensor, idle air control valve, fuel filter. No vacuum leaks.

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  • Answer #1

    Tbone1980 September 11, 2013, 18:59
     Journeyman

    check timing belt, but first check all ignition components, ex: wires, cap, rotor, spark plugs ect..

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    Tom M, September 11, 2013, 20:08
     Rookie

    Thanks for the reply!! Ignition components (plugs and wires) are fairly new (less than 5K miles) and coil tested to spec. No distributor on this car. Compression checked out ... all w/i 5% of each other. Any other ideas?

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    Tbone1980, September 12, 2013, 01:47
     Journeyman

    try testing the plug wires just in case, also check for cracked spark plugs, ignition module, throttle body
    maybe pluged and spark plug gap

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    Tom M, September 12, 2013, 05:16
     Rookie

    Reasonably sure that the problem is not with ignition or fuel delivery systems. Any idea what mechanical issue(s) might cause this problem?

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  • Answer #2

    Greg's Orange Auto (12984 Answers) , Orange, CA - (714) 361-9386
    globalhelper September 12, 2013, 06:11
     Master

    seek diag amd est from a mech. you could have a primary or secondary ign failure

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