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Replaced intake manifold gaskets now Explorer runs like crap.

Discussion in 'Stock 1995 - 2001 Explorers' started by unioncreek, November 8, 2019.

^^Searches ExplorerForum.com^^





  1. unioncreek

    unioncreek New Member

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    I bought a 98 Explorer 4x4 4.0 SOHC with 135K miles. I had to replace the fuel pump before it would run, but it ran great no rattle of the timing chain or rough idling. I kept getting a P0174 code and figured the intake gaskets needed replacing. I did that today didn't have any problems. Started it up and it ran good, CEL wasn't even on. It ran good for about 5 minutes then starts chugging and would barely keep running. Firgured I missed something, but couldn't see anything. So I pulled the upper manifold of to see if I missed hooking anything up. Didn't find anything, put the upper manifold back on. It still runs like its missing checked all the sparkplugs and their conncected. It's also makes a ticking noise on the drivers side rear of the engine also most like a lifter.

    Any help or what I should look at?

    Bob
     
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  3. rasouth

    rasouth Elite Explorer

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    You can spray starting fluid around intake to see if there is a leak. Motor will speed up a little if there is a leak. Make sure your MAF is plugged in. Make sure spark plug wires are in correct position. Disconnect one spark plug at a time to see if there is a change in idle speed. Just a few ideas to try.
     
  4. unioncreek

    unioncreek New Member

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    I just thought of something. When I went to replace the lower manifold, I forgot which way it came off. I put it on and the holes lined up, but I don't know if it only goes on one way. And if it does then the upper manifold is not on right

    Can anyone confirm that the lower manifold only goes on one way.

    Bob
     
    Last edited: November 8, 2019
  5. BKennedy

    BKennedy Elite Loser Staff Member Moderator Elite Explorer

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    Also retorque all of you manifold bolts with the engine warm. My 1994 was running rough with a high idle after I changed upper and lower intake gaskets and that took care of it. Maybe you got a piece of an old gasket or sealer in the valve train.
     
  6. 410Fortune

    410Fortune Snow Season? Staff Member Moderator

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    your 98 has sohc has the two piece intake with a lower plenum and an upper plenum
    Both must be sealed perfectly, there is no iff ands or butts here
    You must clean all surfaces well and the new O rings must be clean when installed. You can use some vaseline to hold them in place and help them seal if needed.
    It sounds as if you may have missed a PCV hose or something or the intake did not fully seat to the engine

    It looks like you are going to have to remove both plenums again and try one more time
    The lower plenum will only fit one direction
    It sounds like something got pinched in there when you did the lower
    As much as it sucks to have to do it again, it is good practice and once you are familiar with this procedure enough you can do the sohc intake in under an hour and that is working slowly and creating a very very clean working space and engine top
     
  7. unioncreek

    unioncreek New Member

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    410Fortune,

    I've pulled the upper off a couple of times, so it doesn't take much. Is there a way to tell which direction the lower goes? I'm going to pull it apart this morning again. I'm wondering if something didn't get in-between the engine and the lower manifold and it's not sealing. I'll keep you updated.

    Where in N Idaho are you?

    Bob
     
  8. 410Fortune

    410Fortune Snow Season? Staff Member Moderator

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    I am 50 miles south of Canada, North of sandpoint

    The PCV connections are below the lower plenum
    there is a plastic Tee connection in the back of the intakes where you are describing the clicking noise, that sucker likes to break easily

    The lower can only bolt on one way, or at least I have never tried to flip it around
    the oblong O shaped holes only line up the one direction
    Also while you have the plenums out you need to inspect them for cracks
     
    Last edited: November 9, 2019
  9. unioncreek

    unioncreek New Member

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    I'm down in Colfax.

    I have it all pulled apart again, good thing I like to tinker. I noticed on the lower that there is an L on one side and R on the other, I'm assuming that L means drivers side. I had it install backwards. I've had the PCV out a couple of times, I'll look at it real close for cracks. I'll check out the upper and lower good too

    Have it back together. Runs smoother, but still is a little rough running. When i first started it it ran pretty smooth, but the longer it ran the rougher it got. Are upper manifold bolts supposed to thread into the upper or slide through it? I'm thinking its not pulling it down tight against the lower because of that. Could a person drill those slightly out so the bolts slide through? I'm going to look it over this afternoon again and see if I missed anything. The EGR valve is a bugger to work around, is it easier to just take if off?



    Thanks,
    Bob
     
    Last edited: November 9, 2019
  10. unioncreek

    unioncreek New Member

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    up
     
  11. 410Fortune

    410Fortune Snow Season? Staff Member Moderator

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    rough running or high idle?
    Check your firing order
    Run it a bit see if it smooths out and sets a check engine light


    The upper plenum screws thread into the lower, do not overtighten! do not plan to make them go "through" the intake either
    metal screw into plastic = careful!!

    If you still have a vacuum leak you will get a high idle, not rough running
     
  12. unioncreek

    unioncreek New Member

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    I went out to check out the Explorer this morning, ran great until it warmed up. Then it started to run rough. I re-torqued the upper intake and it got smoother. It idles smooth and feels like it runs smooth down the road. Checked the plug wires and they were all on. I scanned for codes and there is none. I have the Torque app and it says vacuum is at 24 inches. I'm going to change plugs and clean the sensors on the intake and see what happens

    How does a person reach that passenger side rear spark plug to change it? Almost looks like it would be easier from underneath.
     
    Last edited: November 10, 2019
  13. XLTrunner

    XLTrunner Active Member

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    Access that rear plug thru the wheel well after removing the wheel and splash shield. It's still a bugger to get a socket on it, though.
     
  14. RickOTR

    RickOTR Active Member

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    Check the air inlet hose that goes from the air intake tube to the idle control valve. It's known to tear and leak air. I've installed the lower intake both ways and never had a problem. Try drilling out the holes in the upper intake so that the screws drop into place, not screw in. Too much of a chance of getting them misaligned and stripping out the holes in lower intake causing a leak. Also, check the EGR valve inlet gasket (fel pro 71202) it's prone to leaking, so make sure to grease it before reinstalling the upper intake or buy a new one.
     
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  15. unioncreek

    unioncreek New Member

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    Like the old saying goes "Third Times a Charm".

    Got it fixed. I pulled the upper off, I'm getting good a this. I decided to check that it was fully seating on the lower. It wasn't, there was a small gap at the back large enough to see with my old eyes. Pulled the upper and looked it over real close, there was some crud in the alignment pin hole. I'm assuming it got in there when I had it upside down cleaning it and I didn't notice it. Put it back together and it idles and runs down the road smooth.

    Now to sparkplugs.

    Thanks, for all the help and advise.

    Bob
     
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