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Replace PCV Valve, clean IAC, new fuel filter?

Discussion in 'Under the Hood' started by B94Sport, October 3, 2002.

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    1. B94Sport

      B94Sport Well-Known Member

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      Recently my Ex has been having problems with a very rough idle when I first start it, along with loss of power and reduced fuel economy while driving. I have also noticed that when I stop at lights, the air/fuel mixture reads very lean... I have not experienced the howling described by others whose IAC needs cleaned or replaced, and I am thinking that the lean mixture is a fuel problem...

      Anyone have any ideas as to what I should do to rectify these problems? I know that the PCV valve has AT LEAST 50,000 miles on it (possibly more)... I plan on replacing my spark plugs and wires, replacing the PCV valve, and cleaning the IAC. As for the lean mixture, I am thinking the fuel filter is the culprit (or maybe injectors), but could it be anything else? My truck has 120,000 miles on it... I have made it a habit to use fuel system cleaner every time I change my oil, and I have a superchip and run 93 octane gas, so I assume that unless an injector has failed outright, the injectors should be fine. Any help is greatly appreciated!
       
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    3. TPLYNCH

      TPLYNCH Well-Known Member

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      Fuel Pressure Regulator
       
    4. 410Fortune

      410Fortune ELITE BRONCO2ERER Staff Member Moderator

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      Dont forget these as well:

      CLEAN your MAS sensor

      Replace your fuel filter

      New spark plugs and wires

      Clean the IAC (like you said)

      Also consider replacing the 02 sensors and the EGR valve.

      The fuel pressure regualtor can also cause this.

      Also the lower intake manifold may be loose.

      Start withteh small stuff first.

      Have you tried pulling codes?
       
    5. B94Sport

      B94Sport Well-Known Member

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      I suppose I should have provided more information... The CEL has not come on (and this has been going on for about 2 weeks) so I am assuming there would not be any codes to pull, right?

      I cleaned the MAS about 3,000 miles ago
      Fuel filter history is unknown... It's at least 50,000 miles old
      O2 Sensors have only 15,000 miles on them.
      FPR also has 15,000 miles on it

      So I should retorque the lower intake manifold bolts as well?

      I think I will do the following (based on likelihood of failure due to age):
      Replace the PCV valve
      Replace the fuel filter
      Clean the IAC
      New plugs and wires
      Retorque lower intake manifold bolts

      Anything else?
       
    6. 410Fortune

      410Fortune ELITE BRONCO2ERER Staff Member Moderator

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      I got $5 on the fuel filter....I have had fuel filters give me idle nightmares with my old 2.9L, never on my 4.0L since I now change my fuel filter every year or two. DO NOT USE A FRAM filter, stick with motocraft.

      Do a search for the lower intake bolts, then you can decide if you thinnk it applies to you. 91-94 OHV 4.0L's are NOTORIOUS for having thelower intake gasket fail and the bolts coming loose. Mine were finger tight when I finally checked, tightened them up and I got rid of some rough idle and hesitation problems, took me 10 minutes. If I wasntplanning to build a new engine for my truck soon I would do the full job and replace all the gaskets........
       
    7. Positive Vibes

      Positive Vibes Elite Explorer

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      410Fortune: Where exactly are the lower intake bolts?? I's kinda ingnorant! How many and any other info.
       
    8. 410Fortune

      410Fortune ELITE BRONCO2ERER Staff Member Moderator

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      DO a search holmes, it has been discussed to death and there are even pictures and diagrams.

      If you look at your OHV from the passenger side, and you can locate the fuel rail, they are in there. There are 8 I believe (from memory) and they are 10mm, you will need a 1/4" drive with a wobbly. If you climb up on your engine like I do you can get at all of them fairly easy. You need to follow the torque specs and do them in the right order however........(shhh I didnt use a torque wrench, but I have a good feel for this stuff and was VERY careful not to strip them, steel bolt in aluminum intake = easy to fu&* up)

      These bolts hold the lower intake down onto the engine block, if you have a good idea what you are looking for (what the lower intake is and where) you can find them...........
       
    9. B94Sport

      B94Sport Well-Known Member

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      I attempted to replace my PCV valve. I looked for it where it was suppose to be, underneath the octopus on the intake manifold, on the driver's side of the truck. The only thing that I found in this location that even closely resembled the replacement fram part that I got (part # FV246) has an electrical connector on it and has 2 hoses connected to it which are too small to connect to the new replacement part, which does not even have an electrical connector. This piece is mounted slightly in front of the octopus and below it and connected to a metal bracket that connects to the top of the intake manifold. What is this piece? If this is the old PCV valve, how am I suppose to replace it and if this is not the old PCV valve where can I find the PCV valve?
       
    10. 410Fortune

      410Fortune ELITE BRONCO2ERER Staff Member Moderator

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      The PCV valve on the OHV 4.0L is onthe drives side valve cover, there is a single hose that goes from the vacuum rtee right to it, it is a little white plastic circle.

      I bet you $20 the one you bought at the auto parts store is different from the one you need, seen this happen 100 times. the book at the auto parts store is wrong.

      Pull on the hose it will come off, then you can pop the PCV valve out and take it with you to get the right one.....

      They are normally good for the life of the truck, but I replaced mine anyways since I am **** with my baby and they are $2
       
    11. B94Sport

      B94Sport Well-Known Member

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      Okay, now I feel like an idiot... I looked but could not find it. Do you know where I could find a picture of it, or could someone do me a huge favor and snap a pic of it and post it?

      On a more positive note, last night I pulled the IAC and the MAS. Even though I had just cleaned the MAS 3,000 miles ago, it still had some black crud on it... I sprayed it with some gumout, very gently rubbed the wires with a Q-tip and now the MAS is nice and clean. As for the IAC, man was it a mess inside. After about an hour and a half of attacking it with Q-tips and gumout, it looks completely new inside. No buildup whatsoever. I put those two parts back on, started the truck up, and.... It's a little better, but still has problems. I'll make another trip to the autoparts store today after work to get the correct PCV valve, assuming I can find the original one in my truck :confused:, and pick up a new fuel filter as well.
       
    12. B94Sport

      B94Sport Well-Known Member

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      OH! Another bad symptom (I think) that I noticed last night... While fiddling around with what I thought was the PCV valve, I knocked one of the vacuum hoses loose from the octopus. I went to replace it and realized that it slid on and off waaay to easily. I checked, and it had some kind of fluid inside of it. I could not figure out what it was, but I know that fluid in the vacuum hoses is bad, right? What does that mean? Specificially, I noticed that the two hoses on the rear of the octopus (that connect in such a way that their L joints run parallel to the firewall) had the fluid in them. The hoses I checked on the front of the octopus did not.
       
    13. B94Sport

      B94Sport Well-Known Member

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      How accurate is this picture?

      [​IMG]

      Well I did some searching and it looks like the fluid in my hoses is most likely tranny fluid... I will check for white smoke in the exhaust and check the oil and tranny fluid levels today after work. Looks like I can add a new vacuum modulator modulator valve to the list of things that I probably need.
       
    14. Opera House

      Opera House Well-Known Member

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      Those darn universal PCV's

      I bought one and yanked the plastic two hose tree off it. Then it fit nicely into place.
       
    15. B94Sport

      B94Sport Well-Known Member

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      Good call Opera House... I finally found the PCV valve and replaced it, just by pulling that plastic fitting off of the replacement part. The old valve rattled when I pulled it out, so I guess it did not need to be replaced, but what the hell... It was $2. :) Still having the rough idle problem... The next step will be replacing the plugs/wires and fuel filter. I am still finding fluid in my vacuum hoses, but my tranny fluid level is within the normal range... I will just keep checking it and the oil to make sure neither gets bad, and replace the vacuum modulator valve soon.
       
    16. Opera House

      Opera House Well-Known Member

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      I'm just pulling my 92 tranny out.

      Maybe in a couple of days I can give you some tips on replacing the modulator. I know there is a little pin that you have to get centered. These things are never quite like they say in the books.
       
    17. B94Sport

      B94Sport Well-Known Member

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      Thanks! I have heard it was relatively straight-forward... Takes about an hour and costs $15. I had planned on just devoting a whole weekend to the fuel filter, plugs, and VMV :)
       

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