Misfire

krdadlamb said:

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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wjtstudios said:

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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krdadlamb said:

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....

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wjtstudios said:

Yeah, good point. I was thinking vacuum advance on the timing. But that wouldn’t explain the rotor post.


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krdadlamb said:

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?

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krdadlamb said:

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.

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