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Unsolvable Explorer Rough Idle. Any OBD II experts?

Discussion in 'Under the Hood' started by Cashcrazy, October 26, 2016.

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    1. Cashcrazy

      Cashcrazy Active Member

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      Maybe one is the IAT and one for coolant??

      I am working on a gasket order and don't want to miss anything. Does the EGR have to be removed on mine with the intake?

      Intake orings
      Valve cover gaskets
      EGR gasket(possibly)
      EGR tube oring(possibly)

      Am I missing anything? I know the pid data doesn't point to vacuum leak but I'll replace them to eliminate the orings since it's a known problem
       
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    3. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      When the PCM is in closed loop it continuously cycles the fuel mixture between slightly rich and slightly lean to reduce emissions. The change in fuel mixture will affect the engine speed unless the spark advance and the IAC valve compensate to minimize the variation. As I recall, there is about 1.5 seconds between successive slightly rich peaks. I don't know if the PCM anticipates the engine speed change or if it just reacts to the detected change. I suspect the latter which means the IAC valve and the spark advance will always be "chasing" the desired engine speed. The 2004 and later models have electronic throttle control with no IAC valve. I think a stepper motor is utilized to control the throttle plate opening and the idle (or any other engine) speed. It may be more responsive than the IAC valve but I prefer the simplicity and reliability of a cable with return spring controlled throttle plate. A failed open IAC valve cannot allow the flow of nearly as much air as a failed open throttle plate.
       
    4. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      According to the shop manual drawing the EGR valve is attached to the throttle body. The intake manifold is removed with the throttle body attached so it is only necessary to disconnect the EGR tube from the EGR valve. In that case no EGR valve gasket is required. I see no EGR tube O ring. It should just be a pressure fit since it is high temperature.

      I think since 2000 the IAT sensor is integrated into the MAF sensor for the 2nd and 3rd generation models.
       
    5. Cashcrazy

      Cashcrazy Active Member

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      I read in my chiltons manual that the MAF and IAT can not be replaced separately. I guess they are also saying it's one part. I'll go ahead and get the EGR gasket so I can seperate and clean it out. Just about have my order ready.

      Also, I will start spraying that EGR tube daily with WD40 since I can't replace the gaskets until next weekend. Hopefully that will loosen it up.
       
    6. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Below is a photo of my old, stock 55 mm MAF sensor.
      MAFStock.jpg
      As I recall the vertical wire with the little blob outside and parallel to the cylinder is the IAT sensor. I suspect the little blob is a thermistor. The MAF sensor element is suspended within the cutout section of the cylinder.
       
    7. Cashcrazy

      Cashcrazy Active Member

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      My MAF is the same setup with the two wires.
       
    8. Autolabs

      Autolabs New Member

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      A couple of ideas...
      Unplug the alternator. It is easy and will see how it runs without AC ripple.
      Check resistance of each injector. If the intake is coming off pull the injector rail and pressurize it by turning the key on and look for any drips. Lastly, find a way to check the spray pattern for each.
      Your other thread shows .33 percent misfire for cyl 6. Not enough to throw a code, but enough to feel. So pay special attention to drivers side rear cylinder. I personally won't touch an older Ford idle problem without a known good oem IAC. Aftermarket doesn't put the pintle in the same spot as oem for a given duty cycle and will make you chase your tail. Just my 2 cents.
       
    9. Cashcrazy

      Cashcrazy Active Member

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      What is the resistance spec for these injectors? That's easy enough to check.
       
    10. Cashcrazy

      Cashcrazy Active Member

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      I decided to plug in to the OBD while doing some highway driving. The LT fuel trims were real high running a steady 75 mph.
      [​IMG]

      And I'm with plasticseng. The Bank 2 sensor 2 doesn't look right. I don't know if a failing sensor could cause this. This was taken running a steady 70mph on level ground. I wanted to get data with them real hot.
      [​IMG]
       
    11. plasticseng

      plasticseng Active Member

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    12. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      I agree that the post-cat O2 sensor should not be rapidly cycling in voltage when the engine speed is kept fairly constant. I doubt that the cycling is due to a bad sensor. As O2 sensors age their voltage deviation decreases. There is also the possibility that an O2 sensor's ambient air reference path can be blocked by caked mud shifting the voltage reading but that would not cause a fluctuation. I have a remote infrared thermometer with a laser pointer that displays a digital reading. On a functional cat the outlet temperature will be significantly greater than the inlet temperature. I don't know if a failed cat can result in a rough idle. Your bank 1 and bank 2 LTFTs are identical. Since there is no O2 sensor downstream of the cat that is common for both banks it would be useful to know it's inlet and outlet temperatures. It's unfortunate that the three cats appear to be incorporated into a single Y assembly. The cheapest one Rock Auto sells for that configuration is about $345. I haven't looked under my 2003 Centennial to see if it has the same configuration.
      2003CatAssy.jpg
       
    13. Cashcrazy

      Cashcrazy Active Member

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      I have an infrared thermometer that I can use for getting temps. I haven't paid much attention to the exhaust but I know it has four O2 sensors and would think it should have four cats. I'll try to get the temps for everyone on Friday afternoon.
       
    14. Autolabs

      Autolabs New Member

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      The crazy looking rear o2 signal is a sign of inefficiency on bank 2, not necessarily restricted exhaust. If it is suspect, you should do a back pressure test. It can also be a sign of a slight misfire that the pcm doesn't pick up. If the intake is coming off, then just for giggles, swap bank 1 and 2 injectors. If bank 1 sensor 2 starts to act crazy, instead of bank 2, suspect one or more of those injectors.
       
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    15. Tylers02

      Tylers02 Active Member

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      Don't know if this has been answered already but being I just swapped out my intake plenum, throttle body and egr I thought I would chime in. The egr itself connects directly to the intake plenum. If you want to pull the unit as one i.e. Not take off egr from plenum you just need to unplug connector vacuum lines and the tube that connects to egr. I believe it's a compression type threaded connection so know oring is needed. I got it cheap and egr looks to be brand new plus I think my tps or stepper motor was starting to fail. Throttle response slightly increased, isles good but never really had an idle issue, the most significant improvement was gas mileage going from 9mpg to 12mpg.
       
    16. Tylers02

      Tylers02 Active Member

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      Also if your drive by wire your maf is completely separate from throttle body. It looks nothing like above picture it is square and mounted in intake tube near air box. There is not a seperate portion of tubing that bolts to intake tube. The intake tube has a slot where it slides in and bolts up with two torqs screws. It has a similar mesh screen that streetrod posted integrated into the top portion of the sensor. Hope that makes sense. Basically 1/2" by 3" plastic housing with sensors inside with opening on bottom to sense air flow and mesh screen on the top. This is why it's harder to do the diy cold air intake on the 04 and 05s. You either have to make some type of slotted fitting or deemed out the tubing to the exact size of maf and then secure with two screws. Only thing attached to throttle body is tps and stepper motor. Even the drive by cables were near air box and for sure nothing else installed in throttle body. I installed a bbk 70mm throttle body for a mustang on my 02 and had a intake plenum port and polished to match throttle body.
       
      Last edited: November 4, 2016
    17. Cashcrazy

      Cashcrazy Active Member

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      Thanks for the suggestions. I am pulling the intake off tomorrow for new gaskets. I will pull the EGR valve off for inspection and cleaning. I'll also check the fuel injector resistance, check for injector leaks, etc while torn down. I'm hoping one of these will either fix or find the problem. I debated on replacing the EGR valve while it was out, but I have thrown enough money at this.

      If the above does not fix the idle I may see if an exhaust shop can replace the single down stream converter for $100 or less instead of replacing the whole Y.
       
    18. Tylers02

      Tylers02 Active Member

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      If you need an egr just to test I have my old one I can send you. You can clean it pretty good without taking it off as well. Just put the straw on tb cleaner and spray away. If you have a gun cleaning kit or paint gun cleaning kit you can get it almost spotless. I cleaned the tb, intanke plenum and egr all bolted together but off the truck. Your going to get coolant out of one of the hoses that connects to intake so be ready to plug it. Check your pm
       
    19. plasticseng

      plasticseng Active Member

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      This is good information. I was hoping someone with more experience than me would advise on this.
       
    20. Tylers02

      Tylers02 Active Member

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      I need to take a look I think my 02s have similar readout so also have LTFT that are like 7.5 on 1 bank and three on other and STFT that obviously fluctuate but sometime to low negatives and sometime high positive. I'll try to post the info later so you can atleast compare your messed up reading to my messed up readings.
       
    21. Cashcrazy

      Cashcrazy Active Member

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    22. Cashcrazy

      Cashcrazy Active Member

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      Driver's side valve cover is off and all mating surfaces are clean. Resistance for injectors are:

      Cyl 1 - 17.7
      Cyl 2 - 17.8
      Cyl 3 - 17.7
      Cyl 4 - 17.6
      Cyl 5 - 17.4
      Cyl 6 - 17.3

      No noticeable leaks on the injectors
       
      Last edited: November 5, 2016
    23. Autolabs

      Autolabs New Member

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      Were you able to check spray pattern or did you swap bank 1 with 2?
       
    24. Cashcrazy

      Cashcrazy Active Member

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      Replaced valve cover and intake gaskets. Still rough idle.

      I didn't change the injectors because I didn't have new seals. My options now are to

      1) sell it
      2) buy three new injectors and replace bank two to see what happens. That puts me back to throwing money at it. Both banks still have a higher LT fuel trim just like before. It seems like all of the injectors would be in the same condition.

      I'd like to add that the intake isn't a hard job. The valve covers took slowed me down because I took my time cleaning all the gasket grooves along with the bolts.
       
      Last edited: November 5, 2016
    25. MostlyNewExplorer

      MostlyNewExplorer Member

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      Have you checked the EGR Tube? I had one of the smaller tubes cracked where it attaches to the larger tube down under the heat shielding material. The hoses on those can leak sometimes to, I had to put a small clamp on one of mine.
       
    26. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Can you monitor the knock sensor retard PID? When it triggers on a mechanical noise that sounds like detonation/knock the PCM can very quickly retard the timing to eliminate the knock. I've logged as much as 8 degrees on my Sport. Make sure the contacts on the knock sensor connector mate well and are clean.
       

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