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PO303 and PO316 codes

Discussion in 'Ford Ranger - Mazda B-Series Forum' started by Moranstan, October 11, 2017.

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    1. Moranstan

      Moranstan New Member

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      Year, Model & Trim Level:
      2005 Ranger STX
      2005 Ranger 3.0 STX

      My check engine light comes on if I let it idle with the A/C on. PO303 and PO316
      I replaced plug wires, plugs, coil pack, #3 injector, fuel filter and pump unit and checked injector wiring with noid lights, I also bought the kit to clean MAF sensor and throttle body.
      I really thought the pump replacement had fixed it because it starts easier but I drove it 30 miles after replacing the fuel pump and filter and stopped and let it idle with the A/C on and the check engine light came on. It runs great on the highway but it has a somewhat rough idle.
      What do I replace now? O2 sensors??
       
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    3. Runnin'OnEmpty

      Runnin'OnEmpty Well-Known Member

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      The P0315 indicates a misfire during the first 1000 engine
      revolutions, and is related to the crank position sensor or
      its connection. Since the fault occurs when it gets warm, I'd
      suspect the connector or the sensor itself. You might try
      unplugging and cleaning the connector, and if that dosen't
      help then replace the sensor. I believe it's easily accessable
      on the 3.0 and relatively inexpensive. (Located at the side of
      the crank vibration damper)

      Good luck and let us know the results. The cyl 3 misfire
      should also disappear with the ckps fix.
       
    4. Moranstan

      Moranstan New Member

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      I just put a new crankshaft position sensor on it and it did not fix it. It runs excellent until it warms up, then it runs terrible and eventually the check engine light will come on. P0316 and p0303

      So far I have done the following:



      New crank sensor and cleaned connector

      New injector on #3

      New fuel pump

      New fuel filter

      New plugs

      New plug wires

      2 - New coils

      Checked compression 125 on # 3 - #125 on # 1 - 124 on # 2

      Cleaned MAF sensor

      Cleaned throttle body

      Checked whole engine area for vacuum leak

      Swapped # 3 plug to #1 - no change

      Checked # 3 injector connector with noid light
       
    5. Turdle

      Turdle Moderator Masterbaker Staff Member Moderator Elite Explorer

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      Went through your scenario on an 04 3.0.
      Bad cylinder heads -sunken exhaust valves are common on these engines. The lowest compression cylinder was also the misfire , at 125 psi. Others were in the 140psi range.

      Bad valve on left. You should see no "wall" rising above the exhaust valve.

      New cylinder heads with hardened valve seats are the fix.
      [​IMG]
       
      Last edited: November 3, 2017
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    6. boominXplorer

      boominXplorer Elite Ranger Elite Explorer

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      This is one of the reasons my 3.0 ranger turned into a 5.0. Like turtle said, the valve seats are very soft and I've seen wear as early as 60k miles.
       
    7. Moranstan

      Moranstan New Member

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      If is was a bad valve wouldn't it run bad all the time?? When I start it up in the morning or when the engine has cooled off it runs great, I can drive it 100 mph, no problem, after about 10 miles down the road when I stop I notice a misfire then after stopping and starting the check engine light comes on.
       
    8. boominXplorer

      boominXplorer Elite Ranger Elite Explorer

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      They don't run all that bad with the valves sunken in and 125 psi of compression. They just don't idle well at all. You should be at 160+ psi.

      This miiiight not be your issue but since it appears you have tried everything else 2 different ways it's not looking good.
       
    9. Moranstan

      Moranstan New Member

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      FIXED IT !!!!
      I finally gave up and called my nephew who is a Ford mechanic, I told him everything I had replaced and done. The first thing he asked me was " Did you check the PCV valve ? " I told him no but I would and call him back.
      I pulled the PCV valve and it was completely worn out, it was not checking and you could see light thru both sides of it.
      I replaced it and reset the ECM and it runs perfect. I called my nephew back and he told me " No wonder you couldn't find a vacuum leak, it was internal" He said when the PCV is hung open it will show a misfire, he said that is the first thing he checks on a vehicle with misfires before moving to the more obvious stuff. I hope this helps someone that is having the same problem.
       
    10. boominXplorer

      boominXplorer Elite Ranger Elite Explorer

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      Wow never seen a pcv cause a direct miss but I'll keep that in mind for future.
       
    11. Moranstan

      Moranstan New Member

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      I have never seen a PCV valve so worn out, It was not checking at all.
       

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