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Subaru engine repair questions and answers

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  • ebard
    ebard - 2002 Subaru Impreza - Engine - 1/19/2011
    What is a knock sensor and whats its use
    my engine is knocking
     
    • J and K AUTOMOTIVE TOWING AND REPAIR
      It allows the engine to run with the ignition timing as far advanced as possible. The computer will continue to advance the timing until the knock sensor detects pinging. At that point the computer retards the ignition timing just enough for the pinging to stop.

      A knock sensor assures that you're getting as much power and fuel economy as is possible from your engine.


      knock sensor


      The knock sensor responds to spark knock caused by Pre-detonation of the Air/Fuel mixture. As the flame front moves out from the spark plug ignition point, pressure waves in the chamber crash into the piston or cylinder walls resulting in a sound known as a knock or ping. This is caused by using a fuel with a low octane rating, overheating, or over advanced timing. Sometimes it can be caused by hot carbon deposits on the piston or cylinder head that raise compression. A knock sensor is comprised of Piezoelectric materials; Crystals that when impacted, generate a voltage (same idea as a BBQ ignitor). This voltage is monitored by the computer, and when an irregularity is detected, the computer corrects timing in VVT (variable valve timing) engines, or triggers a DTC Diagnostic Trouble Code) in older vehicles.

  • bill
    bill - 1995 Subaru Legacy - Engine - 1/17/2011
    Check engine light comes on it reads O2 sensor. Both O2 sensors were replaced also gas cap and fuel pressure regulator.
    After each fill up and about 50-60 miles the light comes on again and reads the O2 sensors Bank one. What could be the problem . Also sometimes you can go one tank of gas then the second one comes on.
     
    • yboy82
      1/17/2011 yboy82
      Can you please post the extracted trouble code here? When you replaced your oxygen sensors did you also check (clean if needed) the condition of your electrical connectors and check for battery voltage and ground at the electrical connectors?
  • Cj
    Cj - 1996 Subaru Legacy - Engine - 1/17/2011
    Why does my outback overheat when driving only a block or two? It will idle at normal temp for about 10 minutes.
    The waterpump, radiator cap and thermostat have been replaced. The fans both work. Tried letting any air out by running the engine without the radiator cap on. The heater does not blow hot air. There is no white exhaust or milky oil indicating head damage or a ...
     
    • J and K AUTOMOTIVE TOWING AND REPAIR
      Lower Radiator Hose Collapsing -- A pinched hose (upper or lower) or a lower radiator hose that is collapsing and blocking the flow of coolant when the engine is running can cause engine overheating. The lower hose usually has a metal reinforcing wire inside that looks like a large spring. It s purpose is to prevent the hose from collapsing when the water pump is pulling water through the hose. If this wire is missing or has failed due to corrosion, the hose may collapse.
      J and K AUTOMOTIVE TOWING AND REPAIR
      1/18/2011 Cj
      the hoses seem to be in working order, but will double check the bottom hose. The bottom hose seems to pass water effectively, but the return hose on top does not pass enough fuid to create pressure on the hose.
    • J and K AUTOMOTIVE TOWING AND REPAIR
      *Plugged or Dirty Radiator -- Dirt, dead bugs and debris can block air flow through the radiator and reduce its ability to dissipate heat. Internal corrosion and an accumulation of deposits can also block the flow of coolant. A good way to find internal clogs is to use an infrared thermometer to "scan" the surface of the radiator for cold spots. If clogged, the radiator should be removed for cleaning or replaced. Backflushing the cooling system and/or using chemical cleaners can remove rust and hard water scale, but may do little to open up a clogged radiator.
      J and K AUTOMOTIVE TOWING AND REPAIR
      1/18/2011 Cj
      if the radiator is flushed and water flows effiecently can it still be clogged?
    • J and K AUTOMOTIVE TOWING AND REPAIR
      *Excessive exhaust back pressure -- A clogged catalytic converter will restrict the flow of exhaust and cause heat to back up in the engine. Other causes include a crushed exhaust pipe or a collapsed double wall pipe. Check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system.
    • J and K AUTOMOTIVE TOWING AND REPAIR
      Overheated incoming air -- On older vehicles with a carburetor or throttle body injection, check the operation of the heated air intake system on the air cleaner. If the temperature control valve is stuck so only heated air from around the exhaust manifold is drawn into the air cleaner, it may contribute to detonation and/or engine overheating. Also check the heat riser valve for manifold heat on older V6 and V8 engines. If stuck shut, it may be overheating the intake manifold.
    • J and K AUTOMOTIVE TOWING AND REPAIR
      *Dragging brakes -- A disc brake caliper that is sticking or a parking brake that is not releasing may be making your engine work harder than normal to overcome the friction. Check the brakes and fix as needed.
      J and K AUTOMOTIVE TOWING AND REPAIR
      1/18/2011 Cj
      I dont think the brakes are an issue because it will overheat after a period of time while idling only.
    • J and K AUTOMOTIVE TOWING AND REPAIR
      *Overworking the engine -- The cooling systems in many passenger cars today are marginal and have little excess capacity to handle extra heat generated by towing or high speed mountain driving in hot weather. Replacing the original stock radiator with a larger or thicker radiator can improve cooling capacity
  • subaru
    subaru - 1996 Subaru Legacy - Engine - 1/14/2011
    How to test fuel pump?
     
    • Jason
      1/14/2011 Jason
      Use a pressure gauge, assuming you hear the pump hum when you turn the key.
  • joe
    joe - 1998 Subaru Forester - Engine - 1/8/2011
    Why does my car start missing and a single tapping noise when the rpms reach 5000 when the car is stationary
    i have chaged the spark plugs when im driving it gets to 3500rpm then starts missing and a bit of black smoke out the muffler and the tapping noise
     
    • Nissan Technical Advisor
      Engine misfire is caused by bad spark plug or wires, inspect spark plugs conditions if fouled; replace as needed. Check also the air filter if dirty and replace as required. The tapping noise is the result of low engine oil level or the oil viscosity has lost due to poor oil change intervals or the valve clearance is out of specification. Check the condition of engine oil and correct valve clearances.
    • joe
      1/4/2011 joe
      Hey thanks for that i will give that a go
      joe
      You're welcome, update me of the developments in the future.
    • joe
      1/8/2011 joe
      I have found the problem with my car it was the air flow meter have replaced and is good to feel all the power back in the throttle thanks for all the suggestions and leaves me with the valve clearence specifiation to do.
  • Corey Pine
    Corey Pine - 1996 Subaru Legacy - Engine - 1/8/2011
    Why does my Subaru not start when the engine is hot?
    When the engine is hot and I try to start my car the starter will not engage. There is a clicking but the starter is just dead. It does not necessarily happen every time but often enough for it to be frustrating. If I let the car sit for 15-30 minutes the car ...
     
    • yboy82
      1/8/2011 yboy82
      Did you already check the condition of your starter solenoid and starter relay?
  • tod fleming
    tod fleming - 1998 Subaru Legacy - Engine - 1/8/2011
    Engine running rough and missing with engine light on?
    i changed coil and plugs and plug wires. now getting worse and engine light on and flashing. I checked timing belt and it is in time and new.
     
    • yboy82
      1/8/2011 yboy82
      Did you try to diagnose your vehicle with a scan tool to determine what the stored trouble code in your vehicle is? The extracted trouble code will help you find the fault of your vehicle’s problem.
    • david
      1/8/2011 david
      ck compression
  • Karen Farber
    Karen Farber - 2002 Subaru Outback - Engine - 1/1/2011
    Why does my car stall and shake when i accelerate?
    filled up with gas when tank was nearly empty
     
    • david
      1/1/2011 david
      is it skipping or tires out of balance or (outofround tires)
  • ryan
    ryan - 2004 Subaru Forester - Engine - 12/30/2010
    Found oil in spark plug access hole
     
    • david
      12/30/2010 david
      issparkplugs in the middle of valve cover is the valve cover gasket bad leaking oil into sparkplug hole
  • glarson
    glarson - 1996 Subaru Impreza - Engine - 12/30/2010
    Speed sensor needs to be replaced
     
    • James Vaughn
      12/30/2010 James Vaughn
      there are several spped sensors on most vehicles. which are u referring to? wheel,trans?
  • bob s
    bob s - 2006 Subaru Baja - Engine - 12/29/2010
    Bucking with check engine light on
    car is slightly bucking when stopping and starting at traffic lights,bucking stops when car is in motion,check engine light going on and off. what is causing this?
     
    • david
      12/29/2010 david
      have engine lite tested find what code is in car
    • Friz
      12/29/2010 Friz
      Go to Autozone and they will pull the codes for you at no cost. Once you have the codes, go on google and put in you vechile make, model, year and the codes provided by autozone. It should give you a better indication of where the problem may reside.
  • johnnyrock
    johnnyrock - 1999 Subaru Impreza - Engine - 12/28/2010
    Need to replace fuel sending unit
    how to and where is it. can I get to it going into floor?
     
    • yboy82
      12/28/2010 yboy82
      It’s inside your fuel tank.

      You should relieve the fuel system pressure first by disconnecting the fuel pump connector from the fuel pump relay. And then crank the engine for 5 seconds or more to relieve the pressure. If your engine starts during cranking allow it to run until it stalls. And then disconnect the negative battery cable.

      Remove rear seat bottom, to reach the fuel pump access cover, if not already done. And then remove your fuel pump cover mounting bolts and the cover. Detach tlectrical harness from the pump assembly

      You should label the fuel lines before disconnecting them from the pump. Remove the fuel lines from the fuel pump. Remove the 8 fuel pump mounting nuts and then remove the fuel pump assembly from the tank

      yboy82
      12/29/2010 johnnyrock
      Thanks a lot. This a car I bought and the gas gage doesn't work. Other than that it looks ok to me. Been driving VW's and it's been a while since I've owned a Japanese car. This looks like fun.
  • sthrnone
    sthrnone - 2001 Subaru Forester - Engine - 12/26/2010
    #2 misfire, changed plugs and wires, do not know how to proceed
    186,000 miles, appears to misfire when cold, will go away then reoccurs when the vehicle is hot. just bought the car had to replace valve cover gaskets due to oil in spark plug tubes, replaced cracked radiator and thermostat, changed the oil and replaced air filter, ...
     
    • J and K AUTOMOTIVE TOWING AND REPAIR
      from your question i see one thing you fail to mention is that when you was getting oil in spark plug tubes you did not clean out the tubes so i gather you just pulled out the plugs ? letting the oil to go into the chambers if this is true then you may have fouled out the new plugs i would take out the plugs and reinspect them..............good luck............happy holiday
      J and K AUTOMOTIVE TOWING AND REPAIR
      12/25/2010 sthrnone
      I did the best i could to get it all out...but of course some went into the cylinders...i will pull them out and reinspect them, thank you
    • david
      12/25/2010 david
      ck compression
    • sean
      12/26/2010 sean
      if it has fuel injectors for each cylinder, you might have a bad injector
  • dave99
    dave99 - 1993 Subaru Legacy - Engine - 12/23/2010
    Wont start changed coil still wont start have spark on front 2 nothing on back two changed ing control mod same
    metered control mod have power on 2 of the 4 wires driver side wires dead have spark on front 2 back 2 are dead