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Thread: Cracked manifold = 02 sensor problem?

  1. #1
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    Cracked manifold = 02 sensor problem?

    I have a 96 XJ 4.0 6cyl. Went wheelin down in washington and temp was pretty warm, went into a cold creek bed and I am pretty sure that some water splashed up on the manifold and probably cracked it. Reason being now I have the dreaded sound like air blowing out of a hole or crack in the pipe under the engine when you accelerate.

    My main question is could a crack in the manifold cause problems with my 02 sensors. I occasionally have a slight hesitation in acceleration at about 40 mph then when you give it more gas it picks right up. I think this is due to me gettin stuck in the mud and flingin mud and water all over gods creation and maybe got some in the intake cuz the filter was damp (which I have replaced). I have had people tell me to try and replace the 02 sensors or the TPS but this problem started when the manifold noise started so I think they are linked. So would a crack/hole or bad gasket etc. cause problems with the 02 sensor? Thanks for the help!

    I also replaced the dist. and cap and rotor, and new plugs and wires as well. The hesitation does not happen all the time, just once in a while but it is enough to drive me nuts, not to mention I don't want it to grow into a larger problem.
    F.U.B.A.R

  2. #2
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    The only thing I can think of is that the crack would make the 02 tell the cpu to run lean. Which would cause it to run hot. The hesitation could very well be related but not to my knowledge. If you're looking for a good cheap replacement manifold, look into the APN (auto parts network). It has a life time replacement warranty and will give you better flow. It's 6-2-1 instead of the stock 6-1 for about $130. It's a Banks knock off. Xj manifolds crack all the time.


    http://www.automotivepartsnetwork.co..._manifold.html
    Last edited by Deadman 94 xj; 08-06-2008 at 02:19 AM.

  3. #3
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    my 96 zj has a cracked manifold and it turns the check engine light on when i put it on the code scanner it comes up bad o2 sensor.

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    Correction on my last post, it would cause it to run rich which would foul the 02's causing them to go bad prematurely. What the engine doesn't burn off causes carbon build up in the exhaust. You can usually tell if your tail pipe is thick with black carbon build up, or you might smell a burnt fuel smell from the exhaust.
    I guess that would cause some hesitation.

  5. #5
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    when you replaced your 02 sensors did it help at all with the hesitation you had after you swamped it at seward?
    F.U.B.A.R

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    x2 on the APN... it's a decent replacement!

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    Quote Originally Posted by yamadog257 View Post
    when you replaced your 02 sensors did it help at all with the hesitation you had after you swamped it at seward?
    Mine was always only at low rpms. I never had trouble after 1'st gear. At idle and slow down hill (no acceleration) is when it would want to die out so yours might be a little different. After a couple of months it did it less and less so I can't really say what helped or didn't. The O2's made it run alot smoother but this was around the time that it wasn't really having that problem any more. It was never 100% but it stayed running. Before that I replaced everything that you did and I didn't notice a difference.

    Many people recomended that I replace the CPS (crank positioning sensor) but I had always heard the they die out all of a suddend and don't ever work again so I roled it out. It may very well be the CPS.

    Either way, that cack in the manifold is killing your mpg and replacing the O2's, if you've never replaced them, will help MPG a whole lot. it could fix the problem as well.

  8. #8
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    Did you ever replace the fuel filter? Just a guess but that might have something to do with it.

  9. #9
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    there was a new filter put on it last June, what your explaining about the symptoms at low rpm and idle downhills etc. is exactly what mine is doin. there is no doubt we both had the same problem. I'll try the 02 sensor next week and see what happens. Thanks again!!
    F.U.B.A.R

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