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Old January 25th, 2007, 12:31
wilsmick's Avatar
wilsmick wilsmick is offline
NAXJA Member #955
Join Date: Jul 2004
Location: Portland, ME
Posts: 74
valve carbon or 0331 head issue? 0630 swap?

okay, i have an 0331 head with some pretty severe issues. yes, i've researched thoroughly. also, i'm new to internal engine work and diagnosis. most of what i'm writing i have only learned about in the last few days. don't assume i know stuff (i'm really bad at figuring out acronyms). sorry this is soooo long, but i figured i'd try and get as much relavant info into the first post as possible.

my simple question - WHAT THE HECK CAUSED ALL THIS?

i know i wouldn't bother reading a post this long but PLEASE READ ON! i swear, it's mostly relavant stuff (mostly)

vehicle - 2001 Cherokee Limited - 4.0 w/ 93K - no mods or wheelin trips for this one.
i live in MA, we have 10% ethanol in the gas, i use 87 octane and change my oil regularly. the oil pressure (20psi at idle, 40psi at speed) and temperature (200 to 210) have been fine sine i bought it with 65K. no changes (even through everything you're about to read).

symptoms - the thing is throwing misfire codes like crazy. MIL (or CEL) light blinking continuously unless at idle. the engine feels like its hesitating very badly or missing. it's apparent at idle and all the way through the rpm range - loaded and unloaded. engine vibration is worst under load at low rpm. it is smoother at some speeds and very bad at others, but always there.

all this is happening REALLY fast. it started monday night (3 days ago) and I'm still on the same tank of gas as when all this started. note that the symptoms were present during the injector cleaner procedure. the engine uses no fuel from the tank, only from the cleaner stuff, so its definately not just bad gas or something. at first i thought it was just some moisture in the fuel. i stopped at the nearest gas station and added some dry-gas. it just kept getting worse. at this point, the engine goes into the rev limited safe mode after about 2 mins of driving (maybe less).

i thought the noise its making was a real bad valve tap, but some experienced people have told me that it undoubtedly the exhaust valves not seating. the #1 and #5 cylinders are dead. i can unplug the injectors and there is no noticable difference in the way it runs. the dealer told me they wanted to do their valve rotation procedure (tsb 009-003-03) to fix it. i payed for the injector cleaner procedure and then rotated the valves myself. i saw the tell-tale lines on the valve stems on 5 (1,2,3,4,6) of my cylinders. i also noticed a little milky residue in the valve cover. i did the valve rotation, changed the plugs and the changed the oil and filter (added a pint of Marvel's Mystery Oil). i also had a friend offer to borrow one of the dealer type fog machines to decarbon the combustion chamber. on the way to his house, one of the intake valves started sticking open too (only about a few miles from his house). this is definately most loud and noticable under load.

we fogged it last night and did the injector cleaner stuff again (BG44 i think). the intake valve started seating again briefly during the fog, but towards the end, it wasn't seating again. we took the plugs out to pressure test and do a leak down, but the pressure tester fitting wouldn't reach the plug threads. the plugs (which have about 100 miles on them) are burned black.

so through all the efforts i'v made to fight the supposed carbon issue, the symptoms have just kept getting worse.

i started poking around here and have found lots of "intersting" info about the 0331 head i have. reminds me of the POS Bendix ABS systems they used back in 91. anyway, i'm not sure if the head is definately cracked or not. i haven't noticed any smoke from the tail pipe and its not overheating even a little. i have been noticing some coolant loss. possibly relevant is the fact that i replaced the radiator, water pump, hoses, belt and thermostat last week. (the radiator was leaking, the rest was just for completeness). i figured the apparent coolant loss was due to air pockets filling in the cooling system. still thinking it could be. i'm only talking about maybe 2 to 4 cups since the initial fill.

the main symptoms are the missfires, noise and vibration.

so, off with it's head tonight, and decision time after i see whats really going on.

my options are:
1) valve job on my existing head (assumming no cracks)
2) remanufactured 0331 head
3) remanufactured 0630 head

right now i'm leaning heavily towards the 0630 option (regardless of what i find tonight). making brackets to hold the coil pack rail will be a piece of cake.

has anyone actually done this swap?
will the cam from the 01 work properly with the 0630 head/valve set-up?
will i pass emmisions after this swap? (would love some first hand info in this case, i'm in MA)
do the 00+ exhaust and intake manifolds line up with the ports from the 0630.
anything else you know of that i'd need to watch-out for?

i'm not considering this for the possible hp gain, i just don't like the thought of dealing with this ever again. my last 4.0 (90 xj) made it to about 290K on oil changes alone. what gives?

thanks for reading the whole thing. any thoughts?

'01 XJ, Limited - Stocker (w/ 0630 head)
'89 SJ - 8" SOA, 36" IROKs, High-Steering, Rear Discs, NP208 swap + other junk.
'90 XJ - RIP - 3" lift, 31's (dead, buried, but not forgotten)
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