I've been dealing with a rough Idle and misfires when I start my XJ. It usually goes away when i rev the engine or put it and drive and start moving.

Any ideas what could be causing it and how to fix it?

And as a head up I'm on a strict budget right now since I just lost my job.

 

Hey, I'm not super knowledgeable about this stuff, but my jeep used to rough idle. And what I would do is go through and do your plugs and wires, then cap and rotor on the distributor. What ended up working for me is doing a vacuum line, because vacuum leaks cam cause a rough idle as well. It just isn't fun to find the leak. Good luck!

 

mine did this and the culprit was the ignition coil. it was cracked in multiple places and actually had rust inside of it.

 

When does it happen? After you get the Jeep nice and hot, park it, and restart out about 15 minutes later? If so that sounds like a Heat Soak issue. Heat in the engine compartment when parked vaporizes the fuel in the injectors and/or fuel rail. Do you have the heat shield on the top of your Intake Manifold still? Google it. Plenty of postings concerning this.

 

Clean your throttle body.

 

Clean your IAC as well.

 

Click on the link below and go to Tip 11. Instructions and photos.

www.cruiser54.com

 

If you have a fuel pressure gauge you may want to check that on start up.

 

Well first itd be good to know what year you have. Knowing the year can help us better since older jeeps and newer XJs do have different fixes.

 

2001 sport. 4.0

 

Well I found out that the rough idle is caused by my old spark plugs. so it looks like I'm doing a tune up

 

Are you kidding us?

Your tuneup needs to include plugs, wires, cap and rotor.

 

I already know all of this. Decided when it happened again and threw a code to pull it in my shop and do a diag on it. came out that it needs a full tune up. so I'm going to be doing this during the next week.

 

What's a "full tune up" on a 2001 XJ 4.0? Spark plugs?


Verify the spark plug boots on the coil rail aren't deteriorated when changing the plugs.


NGK Part No. ZFR5N, Stock No. 3459 plugs, gapped to .035".

 

Test compression in each cylinder, replace spark plugs and gap spark plugs to manufacturer’s specifications, check the distributor cap and rotor for cracks and wear. Replace if necessary.