Okay, so I just bought a '96 cherokee about a week ago, and yesterday it started idling kinda funny, theres a lot more vibration than there should be and the check engine light is on. The oil pressure gauge also fluctuates a tiny bit when the engine is idling. When the jeep is moving everything is fine. I took it to a mechanic just to ask what might be going wrong, and I think I'm going to have him find out what code the computers putting out ($20) and just figure out what I have to do from there. He quoted me $250-300 for a tuneup so I think I'll just learn how to do it myself. Does it just need a tune up or could there be something a little more serious going on?

do you have a local autozone? they check the code for free,if your light is on then it's throwing a code..may need a tune up but it's probably something else

Check out this link http://go.jeep-xj.info/HowtoECUcodes.htm Good luck. I hope this helps...Tj

When vehicles run rough at idle, I always check all the vacuum lines, and spark plug wires, first, before I do anything else. You never know...

We have all the codes right here on CF. No need to search elsewhere.
https://www.cherokeeforum.com/showthread.php?t=3323

Thanks for the advise. I took it to a jiffy lube and they diagnosed it for me, it was something about the cylinders misfiring, but all it needs is new spark plugs and im gonna check the wires tomorrow. What spark plugs should I get for it? I know that changing out spark plugs is pretty straight forward but is there anything i should watch out for?

Get CHAMPION TRUCK plugs they work best in a Jeep.

just make sure you get some anti-seeze for the threads...

First, if you look on the firewall, with the hood open, right in front of where the driver sits, there is the recommended plug and gap, on a sticker.

Second, don't just yank on the plug wires, when you pull them out. Pull on the thick part around the plugs, known as the "boot".

Third, only take off and replace one wire at a time. If you get some wires mixed up, it will SUCK to be you. Ask me how I know this....

Get yourself a plug gapper, and learn how to properly gap your plugs. This will pay off in the long run, for you.

Yea, I figured it would be bad to get the wires mixed up. Just out of curiosity what does happen if you mix them up?

The motor just runs rough. The problem is figuring out which wire goes to which plug. It's amazing how quickly you can get your mind upside down over something as simple as that.

WOW I didn't know we had that info on here. I will make a note of that for next time. Sorry...Tj

eh as long as you know where the number 1 plug is on the cap then you can put new plugs on based on firing order..It's not much of a n issue..

...I fixed it. I replaced the spark plugs about 15 minutes ago and was successful. I was a little apprehensive because this was the first time I've ever worked on a car in my entire life, but it worked out. It runs waaaay smoother and feels a lot better to drive. I think that the problem was caused by the ceramic part of one of the plugs breaking off, when I pulled it out it was in 2 pieces and I'm pretty sure it wasn't from sloppy wrenching on my part. Now it's time to deal with all the other little problems...

Good job. If you need help with the rest of your "little problems" then just post up and we will help if we can.