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So this is odd...

Discussion in 'Minivans · Pacifica' started by CudaPete, Jul 1, 2017.

  1. CudaPete

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    Thanks, IC.

    Raining here today so I can't do much but am now leaning towards the IAC valve on the throttle body.

    Van starts and idles in park/neutral fine. Put it in reverse or drive and the idle drops 500 rpm and "chugs" . This is when the code is set.

    Engine revs fine and no black smoke or soot out the exhaust. So, looks like I'll take the throttle body off and give it a good cleaning before throwing any parts at it.
     
  2. CudaPete

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    Hooked it up to a code reader with real time data today. Everything looked normal. Going to remove throttle body and clean it this weekend.
     
  3. CudaPete

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    Another idea that popped up is a leaking EGR valve at idle. Any thoughts on this?
     
  4. CudaPete

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    Here is an interesting observation and this is repeatable.

    Start the car as normal from cold start in the morning and idles fine at 900 rpm in park. Then it warms up and idles at 750 rpm in park. Put it in drive and you get a rough idle at 600 rpm.

    Now here is where it gets interesting. After driving for 1/2 hour I stopped, turned off the car and scanned it. Got 1 pending code, P0172. Started car and let it idles for about 5 minutes. Turned car off and scanned again. No codes. This is repeatable. Get pending code and then no codes. MIL does not turn on, at least not yet.

    Wierd.
     
  5. CudaPete

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    Cleand the throttle body today. It was pretty bad, Also found that the O-rings on the IAC solenoid valve had failed. Replaced them and re-installed IAC solenoid valve. Idles much better now. Drove 40 miles and MIL comes on. P0172. Think an O2 sensor is next unless anyone has any other ideas.

    ThrottleBody.jpg
     
  6. CudaPete

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    Trying to replace the O2 sensor but the old one does not want to come out. Soaked it with penetrating oil, tried cold, tried hot, but won't budge. I don't want to use too much force because O2 socket wants to spread and slip off. Don't want to round off the hex head on the O2 sensor. I'm thinking to cut the wires and use a 6 point socket that I realy torque on. Of course if I do this there is no going back... Any other suggestions.
     
  7. ImperialCrown

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    Heat is generally best for removal. Cutting the wires and using an impact socket is OK if you were replacing it anyways. Use an OEM part.
    Once it begins to move easy or hard, you will know whether the threads are getting damaged or not. There are thread chaser tapss at the auto parts store to clean up O2 threads if necessary.
    I have one for spark plug holes on one side and O2 sensor holes on the other:
    index.php
     
  8. CudaPete

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    So here is the orignal O2 sensor

    old 021.jpg
     
  9. CudaPete

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    We cut the wire, soaked liberally with PB Blaster and warmed up the engine. Then using a 6 point 22 mm impact socket and 1/2" beaker bar we were able to get it out with considerable effort. Threads were okay.

    Old o22.jpg

    Do not use the special slotted socket if the sensor is stuck. It is 7/8 and fits loosely on the sensor which is 22 mm. Also, the special socket tends to flex allowing it to slip off and possibly round off the hex head on the sensor.
     
    #29 CudaPete, Nov 21, 2017
    Last edited: Nov 21, 2017
    somber likes this.
  10. CudaPete

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    Then we installed the new O2 sensor using the special socket.

    New o2.jpg

    Unfortunatley, while this made some improvement it did not completely solve the low idle problem. So we adjusted the mechanical throttle stop on the throttle body. Idles much better now.
     
    somber likes this.
  11. CudaPete

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    So it looks like this is solved. Van is running good, no MIL. It is a multi-step solution for the repair.
    • Remove and clean throttle body including IAC valve.
    • Replace upstream O2 sensor
    • Adjust throttle stop to increase idle, This compensates for mechanical wear on screw tip over the years
    • Add fuel injector cleaner to tank to clean any carbon that may have built up while runniing rough
    You need to do all of these steps.
     
  12. DC-93

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    Just curious: what brand(s) of fuel were used I this van, the majority of the time?
     
  13. CudaPete

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    It varies. I'm not brand specific when it comes to gas. Just stop and get it when I need it. I don't beleve it was a fuel quality problem though.
     

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