Hello everyone!
I have a 97 XJ with 290k on it.

I ran into a bit of an issue that it seem is unsolvable so I am hoping that someone can assist me.

Recently it started idling really rough but goes away completely if it is moving like at all, and throws a check engine light that just says cylinder one misfire.

I have changed everything around the spark plugs and changed out the injectors and this has done nothing.

I have taken this in and gotten it checked twice and no one seems to know why it is doing this.

Any help would be greatly appreciated because everything else seems to be perfectly fine, and I want to keep this thing going for a long long time.

 

It could be carbon under a valve.
I would try some BG44K in the fuel system. It's not your normal cheapie fuel additive.

Add a can to a full tank of gas. Drive til half full. fill with gas and drive til it's at 1/8 tank.

 

My experience with misfires is that they do not go away at speed, you just cant usually feel it. Have they done a compression test and checked your fuel pressure....put a noid light on the injector harness

 

1. Secondary ignition. Replace plug wires, distributor cap and rotor. You mentioned you replaced some stuff but didn't get specific.

2. Fuel pressure. Must be tested with a gauge. The spec for yours is 49 psi, plus or minus 5 psi

3. Noid light good idea to verify you are getting an injector "pulse" from the computer to that cylinder

4. BG44K idea from Cruiser. It's the strongest fuel system cleaner you can buy.

5. Compression test. Spec is 120-150 psi, with no more than a 30 psi variation between cylinders. Can never rule out an internal issue

 

Thank you for all these ideas I have a starting point to go off of with a lot of options.

I will circle back after I check each of these.