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Thread: Misfire

  1. #1
    Been Around the Block krdadlamb's Avatar
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    Misfire

    I have a 98 XJ with the 4.0. Running rough. Throwing misfire codes. I've changed the coil, distributor cap, rotor, plugs, wires and O2 sensor. If anything it's running worse. The only thing I can think of is the timing chain since it has 224,000 miles. Anyone have any ideas before I tackle the big job of changing the chain?

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    Old Timer wjtstudios's Avatar
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    Quote Originally Posted by krdadlamb View Post
    I have a 98 XJ with the 4.0. Running rough. Throwing misfire codes. I've changed the coil, distributor cap, rotor, plugs, wires and O2 sensor. If anything it's running worse. The only thing I can think of is the timing chain since it has 224,000 miles. Anyone have any ideas before I tackle the big job of changing the chain?
    It’s been awhile since I’ve been around one, but they ran a vacuum system, correct? Have you checked for any vacuum leaks? That could definitely be a factor if it does.


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    Been Around the Block krdadlamb's Avatar
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    Quote Originally Posted by wjtstudios View Post
    It’s been awhile since I’ve been around one, but they ran a vacuum system, correct? Have you checked for any vacuum leaks? That could definitely be a factor if it does.


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    I haven't checked anything to do with the vacuum. My reason for leaning towards the chain is the rotor post is clearly only firing on one end, not getting a good contact all the way across. I know the chains are known for stretching, so....

  4. #4
    Knows a Thing or Two Scrambler's Avatar
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    Check fuel pressure as well.


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    Old Timer wjtstudios's Avatar
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    Quote Originally Posted by krdadlamb View Post
    I haven't checked anything to do with the vacuum. My reason for leaning towards the chain is the rotor post is clearly only firing on one end, not getting a good contact all the way across. I know the chains are known for stretching, so....
    Yeah, good point. I was thinking vacuum advance on the timing. But that wouldn’t explain the rotor post.


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    Been Around the Block krdadlamb's Avatar
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    Quote Originally Posted by wjtstudios View Post
    Yeah, good point. I was thinking vacuum advance on the timing. But that wouldn’t explain the rotor post.


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    As I stated, I replaced the rotor and cap, but not the entire distributor nor the cam position sensor. Would either of those make any difference or should I just accept the fact I've got to tear into it and replace the chain?

  7. #7
    Old Timer wjtstudios's Avatar
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    Quote Originally Posted by krdadlamb View Post
    As I stated, I replaced the rotor and cap, but not the entire distributor nor the cam position sensor. Would either of those make any difference or should I just accept the fact I've got to tear into it and replace the chain?
    I hate to have you throw parts at it, but all three I would guess would cause the misfire. I don't know enough about that engine to say for sure, it would be a hell of a lot easier to try a new distributor and or a cam sensor first before you tear it down. Nothing worst tearing the engine down to do the chain to find out it was one the other two!! I wish I could be of more help, good luck.
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  8. #8
    Been Around the Block krdadlamb's Avatar
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    Update

    I went ahead and did the timing chain, it was definitely stretched. But didn't fix the problem. So I checked the compression. Started on cylinder 1, it only had 50, 2 had 120, 3 didn't even register, so I quit. I'm hoping it's just valves and not a piston.

  9. #9
    Nothing but a Thing Snboarder113's Avatar
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    Was it knocking or slapping?


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    Old Timer wjtstudios's Avatar
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    Quote Originally Posted by krdadlamb View Post
    I went ahead and did the timing chain, it was definitely stretched. But didn't fix the problem. So I checked the compression. Started on cylinder 1, it only had 50, 2 had 120, 3 didn't even register, so I quit. I'm hoping it's just valves and not a piston.
    Yeah, that’s not going in the right direction. Good luck


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