Hello all,

I have a 1998 Jeep Cherokee with 290k on the clock, the other day I revved it probably a little too much, maybe around 4500-5000 at most (nothing I haven't done before), and after coming to a stop noticed I had some weird vibes but only at idle with a noticeable noise.. After getting to my destination and leaving I pulled a CEL for misfire on cyl 1. This is about the fourth time in a couple of years and have been able to clear it with a new spark plug. So naturally I went and did a tune up, plugs,wires, cap, and rotor and that fixed the CEL but hasn't fixed the vibes at idle. I have had a cracked exhaust manifold and noticed it had gotten worse. Ordered a new and reset the ECU in an attempt to get new fuel mapping. So now the noise is gone but I still have the noticeable vibes at idle. It has gotten slightly better and after replacing the manifold the noise is gone. I do have poly bushings in my motor mounts. It seems to drive and accelerate fine with no noticeable decrease in power or smoking and its too early to tell if my gas mileage has decreased but will update. It does not surge or seem to want to die at idle, just vibrates. My boss mentioned it could have a burnt valve... I inspected the valves (from what I could see with the manifold off) and it looks like it has got a little oil on the exhaust valve compared to cyl 2 which looks a little dryer. Just curious what some suggestions might by? I have not tested any sensors so far. But the issue with the vibes only seem to occur at idle and are worse in drive compared to neutral and park.

Thanks guys for any suggestions! Sorry if some of this is a run on.