Hey folks,

I've had a 2001 Cherokee for a couple months now and have had several issues. Three weeks after getting it, got CEL for multiple cylinder misfire, replaced spark plugs and got new coil pack, noticed coolant was missing, turned out to be cracked cylinder head. Got that fixed, drove it around a bit without problems. Driving to my parents (~180 miles) got CEL codes for cylinder 2 and 3 misfires and catalyst efficiency 2-1. Changed spark plugs (dealership didnt bother getting new ones with cylinder head replacement), ran great for about half a day, then got codes for cylinder 1 and 2 misfire and catalyst efficiency (p0301, p0302, p0432). Got oil changed to make sure all the rest of the crud from the cracked head was flushed out, along with a coolant system flush, started idling rough (at around 400rpm) and near-stalling. Read it could be crank position sensor, changed it, no dice. Just removed throttle body, was pretty clean but I cleaned it and IAC extra just in case, no improvement. Was going to do a seafoam treatment according to this tutorial: http://diysrc.com/how-to-seafoam-you...arbon-buildup/ but buddy of mine warned me it would probably wreck my bearings so I guess I'm not going to do that. My next idea is to switch out injectors (have read the 4 hole nozzles give improved performance anyway) but other than that, I'm out of ideas. Is it possible I got a faulty coil pack? Did I somehow manage to destroy the bulletproof i6?

 

O2 sensors sending bad data can cause most of these symptoms. If the battery has been disconnected recently, the engine management may have been reset improperly. I am not familiar with the Cali emissions XJs but you could have a bad catalytic converter (if my memory is correct on the EPA emissions XJs 0301 and 0302 are the O2 sensors just before and after the catalytic converter. From what I have read seafoam does next to nothing for the 4.0 engine. Poke your head in the engine compartment and around the emissions system and start diagnosing, you can "rent" most diagnostic implements from local parts stores for a refundable deposit. Welcome to the forum.

 

How exactly?

 

Got a new cylinder head from Clearwater cylinder heads, supposed to be a different cast from the 0332 and less prone to failure... My initial suspicion was that it failed again but there's no coolant loss this time and I have not found any signs of coolant in the oil (and no overheating). Got the higher end felpro gasket set in an attempt to avoid future issues as well.

If I were to go ahead and switch out all four O2 sensors, are they all the same part number? And what kind of time would I be looking at to replace them all? (Cant be any worse than that freaking crank position sensor).

 

Different part numbers. See pic below for NTK part numbers and positions.

 

If you're interested in chasing O2S sensor faults check the O2S heaters RELAYS fuse in the PDC.

 

Sweet, I appreciate it guys. I'll switch em out and see if that does the trick (figure at 130k miles they're probably due anyway)

 

I would diagnose before replacing all your O2 sensors.
Gentleman,after a head swap doesn't the CPU need some miles & start ups to relearn correct operation?

 

I suppose so, light went off on my way to parts store to get O2 sensors. Problem solved! (hopefully)

 

CCCKen - Hey! Can I post that PDC picture up on my website? The one I have up now isn't labeled and I'm lazy. http://www.lunghd.com/Tech_Articles/...tification.htm

laytox (& anyone else) - If you need to clear codes or see what's going on with your sensors; I picked up an OBD2 bluetooth code reader that does all kinds of stuff besides just scanning & clearing codes. (With the Android app Torque (free version) it will even look up the codes over the net!) It also allows you to track darn near every engine and sensor function on the fly - rpms, air/fuel mix, O2 circuits, etc, etc... It's under $11 at Amazon: OBD2 code reader for use with Android phones

There's also a more expensive WiFi version for use in a shop but my phone is with me all the time vs a laptop or desktop. Even my code reader came with a disc for XP that had all kinds of software (dyno type stuff) but I never used it.

 

That is awesome, ordering one right now. Thanks for the heads up!

 

No problem! It really works great on the OBD2 vehicles I have (a chevy van & GMC Jimmy).

Visit the Google app store and get Torque (FREE). It's great - you'll play with the darn thing for an hour just making up 'dashboards' when you get it. You can actually set up an android tablet with a speedo, tach & other gauges from this thing but I just set up my phone with RPM & MPG when I'm trying to milk some miles from my gas pig of a van.

 

Laylox I'm in the same boat you were in with a cracked head. I just confirmed it today and I'll be following your posts.

Ccken, thank you for posting the labeled fuse box. I pull the cover and was checking it out thinking it would be nice if they all were labeled. Also the identity and location of the 02 probes. I'm sure I'll go down that road someday and that's good info for a first timer.

 

Sure.