XJ_Lemp

Hello fellow XJ owners, I've just completed some pretty serious engine work that has dragged along the past two months. Work and post work responsibilities take time...enough of my life story and into the bizz. I have replaced the following on my XJ all at 179,972 miles.

New: water pump / oil pump / Clearwater head / NGK spark plugs / Brown Dog rubber motor mounts / Crown trans mount / 4 hole injectors from fellow forum member jhc7399 / coolant hoses / valve cover breather grommets / radcap / oil pressure sending unit / oil filter adaptor o-rings / rear main seal/ felpro headgasket/ intake manifold gasket / oil pan gasket and some other gaskets.

That being said I tried to do my best to follow all the torque specs for nearly every bolt I locked down. After getting the XJ all back together I started her up and boy was she shaking like my Cummins. Some of you may say that I'm getting vibes from the new mounts. This is true however while listening to the engine and at increased RPM something seems off. My exhaust kinda smells like raw fuel and at idle I believe I can hear a miss. As RPM's increase it smooths out A LITTLE but I believe its still missing. I have tried cracking the injectors and 2-6 for sure change the idle of the engine. I am having trouble determining if injector 1 follows the same trend as the rest. When I had the intake manifold off I gave all the sensors a shot of intake cleaner. I do not think that I have any vacuum leaks. I added a touch of dielectric grease to the majority of the electrical connectors before reinstalling as well. Another factor maybe that I removed and reinstalled my Camshaft Position Sensor that drives the oil pump. I did follow the steps to line the two holes up so that the timing is correct. This could just be another factor. I am somewhat stumped and not sure where to begin.

Sorry for the long read, I just want to provide as many details as possible. By the end of the week I will get some videos up to give everyone an audio/visual! Thanks for the help fellow XJ crew!

PatHenry

If it were me, I'd start by looking at the following:
1 ) Wiring condition for the coil rail. If this got tugged or twisted there's a chance something came loose. Also it's reported that these wires can chafe, so something not right there would cause any number of "missing" type behavior and unburned gas.
2) The condition of wiring for all the injectors. Same sort of concern.. if these are incorrectly firing, missing and gas smell are possible.
3) Did the IAC get jostled or anything? Unlikely, but worth checking.

If the wiring is all sound, I would consider 2 things that are more involved/work:
1) Swapping the old injectors back in and seeing if it has an effect.
2) Testing/checking the spark for all 6 plugs. This requires some work to set up the testing, but it would be great to know if/that you're getting solid, strong and consistent spark across all cylinders.

Maybe someone smarter than I has better advice, but that's my take.

Keep us posted!

PatHenry

Also be careful gas isn't getting into the oil -- It'd be a shame to do all that work to have bearing failure due to contaminated oil.

mattheww97

My bet would be something electrical. I see far to many guys on here with a misfire and everyone throws parts at it rather than doing simple free electrical tests this nobody ever solves them.

Not sure what year your XJ is but my misfire ended up being a combo of a bad coil rail and a shorted wire at the oil pressure sender. (00 XJ). Could have easily figured this out for free but instead I chose to throw parts.

XJ_Lemp

Thank you for the replies guys! I did a quick injector swap (old ones in) and there wasn't a difference in how it ran. Installed the 4 hole injectors back into the Jeep. I keep track of the suspect injector that I previously mentioned and sure enough I've found that it doesn't change the idle when it's unplugged. So I believe I have a faulty injector. However this still doesn't solve my problem. I am going to try and get a couple videos of the Jeep up here tonight. I'm also going to look into inspecting the coil rail. My fuel is about two months old...could this be a serious factor? (I know dumb question but I gotta ask) Keep an eye out for those videos! Thanks again


2001 Cherokee XJ sport 179,792 miles.

XJ_Lemp

I do not believe the IAC was beaten around. It was out for all of 5 minutes and then right back in it went.

PatHenry

2 months isn't that long for the gas.

Is the injector issue the actual injector (if so I'm sure Jeff will take care of you - he's a good guy) or the wires?

It sounds like you're saying you have both a rough general idle and the stated bad injector.
You aught to be able to run 6 good injectors between the old and new set (not ideal, just temporary) to diagnose and test the idle.
Did you check the coil wiring? Gut feeling is you're getting a short or dis-continuity in the wiring/connector considering the coil probably didn't just coincidentally fail right when you were replacing the head.

PatHenry

I might pull it and verify the o-ring didn't get lost/damaged.

​​​​​​​Also, is there any chance the intake or exhaust manifolds cracked during the replacement?

XJ_Lemp

I am positive the injector is the issue. I swapped #1 and #2 injectors and the issue followed the injector...it did not remain in cylinder #1. I have no had the chance to dive into the coil wiring. That is going to be tomorrow's first project. I am also going to look into that IAC o-ring. I don't remember seeing one but I could be wrong. I did try to the key trick to check for codes that are stored...I got nothing. I did not see any cracks on the intake manifold or exhaust manifold. I believe I have the Mopar updated exhaust manifold. It is two piece and is rippled (for lack of better wording) at the bends. My Cherokee came off the line in August of 2001. Thank you PatHenry for all you input! You've been very helpful and it's much appreciated. I'm still working on the videos. I not gifted with technology lol. Thank you again Lads!

XJ_Lemp

UPDATE:

I double checked the IAC o-ring. It was still in place and intact with no visible issues.

I pulled all the spark plugs for inspection. Everyone one was gapped properly. They all also displayed signs that they where emitting a spark.

I pulled the coil rail. Upon visual inspection all the boots where seated correctly and in good shape. On top of that the plug and it's wires did not appear to have any issues either.

I tested resistance of the coil rail. I checked the resistance between #1 & #6 / #2 & #5 / #3 & #4 - all tested at just above 1500 ohms. From what I read on Jeep Forum this is a healthy number.

So I believe I can rule out the coil pack itself as an issue. I there anyway that my timing could be slightly off? I did have to reinstall the Cam Synchronizer Sensor after I finished putting on the new head. Is there a possibility that I did not have the engine perfectly at top dead center?

For some reason my computer will not let me upload the videos. Still working on solutions for that issue.

Thanks everyone for their input and penitence!!!

XJ_Lemp