When I start my engine I idle at around 500 Rpm and if i pop the hood i can see the engine shake a little bit. When I first start accelerating it will sometimes just jerks forward. I haven't owned the jeep long so I'm not entirely sure how long it has been since it's had the spark plugs checked but I'm also wondering if the O2 Sensor may be going bad.

 

How does it run after its warmed up?

 

It runs the same. It seemed like it just started getting worse today. I went somewhere and when I got back in to start it it had a very rough idle and did that a couple other times that day. Then I let it sit for a while and went back out. I started it again and it didn't seem as rough but it still idles at a little over 500 RPM.

 

How many miles are on it?

Might be time for a tune up. Is your check engine light on?

 

No check engine light.

About 102,000 on it.

 

probably the plugs a bad o2 sensor usually throws a code

 

Well that clears that up then. I'll change the plugs next week.

 

Yeah plugs are the cheapest, and at 88k mine still had the original plugs and they were pretty bad although it still ran fine. If you still of the old plugs, they're probably real bad.

 

I haven't owned the car long but I won't be surprised if I open it up and see the originals.

 

what year is this xj? If it's older than 91 it won't have the check engine light.

But if your avatar is yours then it must be a 97 or newer?

You should still check the codes even if the check engine light isn't on. It will definitely give you an idea of what to start with other than a tune up.

 

yea if it was the o2 it would be worst with the affects right now i have a bad o2 an it throws my stuff out of wack like loss of power an all that bs i replaced the o2 an it was fine do your plugs wires an cap just to be sure

 

Changed them today but it still idles at 500RPM in drive, about 750 in park. I'll probably look for vacuum leaks tomorrow.