Check engine light

[Hercules]

So I took the jeep in to Brake Check to have them do a diagnostics check and once over on the vehicle just to see where I stand (upon arrival no check engine light). Also got the oil changed in the process cause I was there and lazy. After trying to sell me everything in the book I go with a fuel system cleaning cause I'm sure it needs it. The computer diagnostic test detected a number 5 cylinder miss fire. Now my check engine light is on and the guys at Brake Check did not know why. Wondering if you guys can give me some guidance on what I should do or check. Thanks.

PS: I'm only doing my own work from now on. Even if I break it at least it got broke by someone who didn't know what they were doing.

[Mudderoy]

So I took the jeep in to Brake Check to have them do a diagnostics check and once over on the vehicle just to see where I stand (upon arrival no check engine light). Also got the oil changed in the process cause I was there and lazy. After trying to sell me everything in the book I go with a fuel system cleaning cause I'm sure it needs it. The computer diagnostic test detected a number 5 cylinder miss fire. Now my check engine light is on and the guys at Brake Check did not know why. Wondering if you guys can give me some guidance on what I should do or check. Thanks.

PS: I'm only doing my own work from now on. Even if I break it at least it got broke by someone who didn't know what they were doing.

If I remember correctly the 2000/2001 4.0 engines have a heat soak issue that causes a misfire. I was thinking it was cylinder 3, but I'm just going on memory here. I believe those year model 4.0's have a heat shield on the injectors to help keep this from happening.

Now I personally have had an issue with the harness rubbing on the fuel rail nearest the firewall. It rubbed through one of the wires and was causing a ground condition. This in turn caused a misfire code to the ECM. The fix was simple. I just used a tie wrap to lift the harness up off the fuel rail.

[NW99XJ]

So I took the jeep in to Brake Check to have them do a diagnostics check and once over on the vehicle just to see where I stand (upon arrival no check engine light). Also got the oil changed in the process cause I was there and lazy. After trying to sell me everything in the book I go with a fuel system cleaning cause I'm sure it needs it. The computer diagnostic test detected a number 5 cylinder miss fire. Now my check engine light is on and the guys at Brake Check did not know why. Wondering if you guys can give me some guidance on what I should do or check. Thanks.

PS: I'm only doing my own work from now on. Even if I break it at least it got broke by someone who didn't know what they were doing.

So I see you have a 2001 with the 4.0L ..... and it was just "serviced" by a brake shop that did an oil change and fuel system cleaning.....
The first couple things that come to mind, is going to be to look over the obvious...check the spark plugs, make sure they are torqued down, ensure the plug wires are on good & tight.... and possibly even check the resistance of the #5 cyl. wire against one of the same length (if possible) Also check the cap & rotor, look for signs of wear/corrosion....
I would also consider asking the shop HOW exactly they did the fuel sys. cleaning, ..... did they remove any of the injectors? IF so were the O-rings replaced? ..... Also what sort of chemicals were used, and what their policy is for what happens when something is dislodged from the fuel system and cloggs one of the injectors.
This stuff is a good place to start, and will at least get the ball rolling on the troubleshooting process.

[4.3LXJ]

I agree, find out what they did. The fact you left with the light on and they don't know why is bogus