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91-94 Stock Air Box - Filter - CAI - and more

Discussion in 'Stock 1991 - 1994 Explorers' started by Tbars4, April 6, 2009.

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    1. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...This is for all the 91-94 Explorer/Ranger owners looking for answers on their Stock Air Box setup, Filter options, adding a CAI (Cold Air Intake), and for those who want to return their Intake Air System back to stock and don't know where to begin....
      _________________________________________________________________________

      ...The 91-94 Explorers/Rangers have what is called a Thermostatic Air Cleaner, Intake Air System and is an important part of your Emissions system...If you do not have this in proper working order, you will fail both the Visual, and your Emissions Test....

      Thermostatic Air Cleaner

      The below info can be found here and is used just to describe the following...
      http://www.wivip.com/index.html?te_idletest.html

      The Thermostatic Air Cleaner System is an early emissions control device that was designed to deliver temperature-regulated air to the intake manifold such as warm air for cold engine conditions and cool air for engines at normal operating condition. Thermostatic Air Cleaner systems usually consist of an enclosed air filter housing, with an air intake snorkel containing a thermostatic control valve. This thermostatic control valve controls whether cool air or warmed air enters the intake manifold through a vacuum signal. Later models have used electrically activated thermostatic control valves. After the engine has reached normal operating temperature, the thermostatic air control valve returns to a position to allow cool air to enter the intake manifold for normal engine operation.

      Thermostatic Air Cleaner items checked:
      1. Exhaust shroud is missing or not secured properly.
      2. Heat riser tube, cold air duct, air cleaner cover, plugs, flexible material between air cleaner and vacuum motor, is missing, broken, plugged, taped or disconnected.
      3. Vacuum lines or hoses are missing, broken, plugged, taped or disconnected.
      4. Air cleaner is missing or "unsealed" for a Pulse Air type system. Wing nut(s) missing.
      5. Vacuum motor port is not properly sealed (if dual snorkel).

      These pictures show how your vacuum lines properly hook up and also the locations of it's parts...

      ...This is where your 2 vacuum lines connect at the top, rear of your Stock air box lid..(The bottom half of your airbox is mounted on top of the right front fender) This lid fits on top of that piece...
      [​IMG]

      ...This is a pic of the underside of your stock air box lid...Note the vacuum port on this side...Nothing connects to this...(But on the top side of this port is where the vacuum hose for the thermostatic control valve connects)
      [​IMG]

      ...This picture shows the proper placement of your vacuum hoses...
      [​IMG]

      ...And last but not least, this is your Thermostatic Control Valve located in your Cold Air Intake duct...It is located behind the passenger headlight and most people can only see the vacuum hose heading down to it...Be sure this hose is connected...
      [​IMG]

      _____________________________________________________________________

      Stock Air Filter Options

      ...In this picture the top filter is an STP filter which comes designed with a ridge that keeps all the individual pleats from closing together...The bottom filter is a Fram air filter...I have found that these tend to close up and clog when they are in a real dirty/dusty environment...This shows the bottom, pleat side of the filter...
      [​IMG]

      ...This is the top side of your air filter...The fresh air is drawn in from the bottom of the filter, througt this top side of the filter, to your MAF, on through the duct, and to your throttle body...(Again, notice the pleat separation from the STP air filter)
      [​IMG]
      _______________________________________________________________________

      Optional Cold Air Intake (CAI) Upgrade

      ...There are several models to choose from...K&N and KKM, are 2 of the most common to be found on Explorers...I have the KKM that was designed for our motors...Here is a link to their site... http://www.kustomz.com/054094.html

      They have installation info so, here is a pic of my setup...The KKM filter pretty much sits just above the bottom half of the stock airbox and attaches to the existing tube...It takes a whole 10 minutes for the swap to stock for the smog test..:biggthump (Note the capped off vacuum line from the motor, the one with the bolt in it)
      [​IMG]

      [​IMG]

      Note:...If you live in California, these will not pass Smog

      Is the True-Rev Induction kit emissions legal in my area?

      The True-Rev Induction Kit is designed for competition use and though it does not eliminate any required emissions devices, it does not carry any emissions exemption certificates. The bottom line is check with your state testing stations for guidelines on engine modifications. Our Kits are not C.A.R.B. certified.

      ...And here is a link for C.A.R.B...;)
      http://www.arb.ca.gov/homepage.htm
       
      Last edited: April 9, 2009
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    3. cybergasm

      cybergasm B

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      so umm did you pass?........
       
    4. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...Why yes, yes I did...:bounce:

      ...Except in my rush after fixing my CEL problems, I almost forgot to swap my Stock filter back in...:rolleyes:
       
    5. cybergasm

      cybergasm B

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      cool My turn comes up next week :D
       
    6. DeRocha

      DeRocha NEX Vice President Staff Member Moderator Elite Explorer

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    7. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...Thank you for adding that great video...:biggthump

      ...Is that you speaking on the video???..:scratch:
       
    8. DeRocha

      DeRocha NEX Vice President Staff Member Moderator Elite Explorer

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      Your welcome :) I hope it adds some info to this thread which you did a great job at creating.. :thumbsup: I certainly can appreciate the time and effort that goes into creating a well thought out, articulate, and visually pleasing thread . And yes that is my voice on the video clip (Narrating a video is something I'm not the best at.. obviously )
       
    9. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...You did Great ..;)

      ... I would have never thought of doing a video on that , but it is probably the most important and highly overlooked item of this particular system...

      ...And Thank You very much for the high praise...:notworthy
       
    10. Verno

      Verno Active Member

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      Both you guys are awesome. Really simplified the process of figuring out those two vac hoses for me! Gonna look at the Ex when I get home tonite.
       
    11. boggs1227

      boggs1227 Well-Known Member

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      thermostatic control valve / sensor (Air Cleaner Temperature Sensor ) :

      duralast brand

      auto zone part number # E108

      price $ 11.99 est' (may be diff from state to state )
       
    12. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...Thanks for adding that...I'm sure it will help others locating that part as these tend to go out over the years...:biggthump
       
    13. rustbucketMI

      rustbucketMI Active Member

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      Thats a lot of money for a filter and a flange adapter.

      My CEL had been coming on for about a year, gave the truck to my brother for a while and didn't care to fix it, so i decided to replace the MAF that had gone bad. Instead of using the stock MAF housing i went to teh junk yard and pulled a MAF out of a 4.6L T-Bird and replaced the sensor with a new 4.0L sensor i bought. I went to my local autozone and bought a spectre cone filter. All in all i spent $25 on the cone filter, $10 on the sensor on ebay, and $30 on the MAF housing (would have been $10 but i didn't have safety torx to get the 4.6L sensor off).

      For this $65 i got a new MAF, essentially the same cold air setup and the KKM or K&N and approx 50% better air flow. This results in a lot more power. For kicks i put the old housing back in and felt a very noticable difference in power.

      Instead of plugging the vaccum line i put the whole thermostatic control valve and vaccum line on the air tube after the MAF. There is essentially no difference in air properties on either side of the MAF. I didn't know about the control valve so i obviously didn't do anything about it.

      Since my mod i havn't thrown a CEL and my power is great. The gas millage is about the same but with the added power im having trouble keeping my foot out of the gas. I dont have the misfortune of have to be inspected every year but as far as i know my emissions havn't changed. I've had this for about 5 months and absolutly no complaints. Just a suggestion for a cheap easy upgrade as opposed to paying for more for less
       
    14. seth247

      seth247 Well-Known Member

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      Great info.

      small correction.

      You say that the air is pulled into the top side of the filter but I beleive it's the other way around.
       
    15. Four0Sport

      Four0Sport Elite Explorer

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      eh that sounds bout right to me
       
    16. YourNameHere

      YourNameHere Active Member

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      I did something very similar.

      I went to the boneyard and grabbed a 5.0 MAF housing. This housing doesn't require an adpater to clamp on a filter. The conical filter just slides right on. I already had a K&N filter, so I just slid it on the end of the 5.0 housing and clamped the filter on. Reattached my stock MAFS, and i was good to go.



      Great write-up!
       
      Last edited: April 30, 2009
    17. DeRocha

      DeRocha NEX Vice President Staff Member Moderator Elite Explorer

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      Just to be clear for others reading this thread: If you remove the stock air box in favor of a cone type of filter the Bi-metal sensor and vacuum lines are no longer needed (just plug the lines). Routing warm/cold air to the stock airbox does very little anyway, and provides Zero benefit when using a Cone filter.
       
    18. safn1949

      safn1949 Active Member

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      That was my next question,thanks.:D
       
    19. jtb1689

      jtb1689 Active Member

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      Don't know about other states, but here in Washington State, in one of the bigger counties where they require 2-year emissions testing (no visual, just numbers/diagnostic) I took out every part of my old air box system including the part that goes from the headlight area to the airbox with the thermostatic air flow part when I put in my KKM and passed with flying colors. I've actually passed twice. Once just one year after I installed it and again just recently (3 years after installation)
       
    20. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...Then this thread will be a great reference in the future..;)

      ...It is very common as people will pull out their stock boxes and want to return it to stock when they sell the vehicle...The questions always come up on where the hoses are going and coming from...

      ...It is good to save your stock items and reinstalling them when you sell the vehicle...That is how I got my KKM filter for cheap....

      ...Again, thanks to HappyGilmore....:biggthump
       
    21. DeRocha

      DeRocha NEX Vice President Staff Member Moderator Elite Explorer

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      Just to be clear the thermostatic air control is only used to warm up your engine a few minutes faster than normal. This equipment saves maybe 1-2 gallons of fuel over the course of a year. Obviously not a huge deal, but when you add in a few million vehicle you can see were things make a difference at the global level. Anyway once your engine reaches Normal temp your emissions will be the same with or without the thermostatic temperature system, so its no surprise you passed your emissions test.
       
    22. Four0Sport

      Four0Sport Elite Explorer

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      Ted, this needs added to your list of useful threads and how-to's. it took me 10 mins to find it for a reference! lol
       
    23. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...It's in that list.........................Now it is.................:D


      ...Actually, I am going to, in the future, do a thread with a list of just my useful thread's and "How To's", but for now I've included it in the one in my signature...;)
       
    24. Four0Sport

      Four0Sport Elite Explorer

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      ok.. i ran through there earlier but must have overlooked it.. i had to resort to looking at all the threads youve posted in, 523o4iu3 pages later i found it lol

      and as always, thanks for all the useful info
       
    25. Tbars4

      Tbars4 Offroad/Fitness Moderator Staff Member Moderator Elite Explorer

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      ...Lol....I just posted it as soon as you asked...:p:
       
    26. jordan1948

      jordan1948 Active Member

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      Anybody know where I can find just the "adapter" for the cone filter that bolts onto the MAF? I don't want to make one if I don't have to ya know.
       

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