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Old 02-05-2014, 01:36 AM   #1
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P0304 P0300 Leak-down and compression test results

1999 Jeep Cherokee sport 4.0 AW4

So I have been getting p0304 and p0300 CELs every once in a while. It seems to go along with rough idle at times. When its under load it feels fine. I'm riding on 37" tires so its pretty slow to begin with, never noticed a significant decrease in power. I decided that after doing some research on the forums I would try a leak down test and compression test. Here are the results:

LD.............C-D.C-W
#1 - 5%....148 160
#2 - 5%... 159 170
#3 - 29%..145 156
#4 - 41%..135 151
#5 - 7%....165 170
#6 - 8%....151 170

So as we can see from the leak-down, there are problems in cylinder #3 and #4. When doing the leak down, both cylinders had leaking out of the exhaust pipe. All cylinders showed minimal leaking out of the crankcase, it was barely noticeable though. I was planning on just buying a reman head from www.headsonly.com . Comes with valves and springs preinstalled for $345 shipped. I thought that until I did the wet compression test on cylinder 3 and 4. By the way, the wet test was done warm and with a capful of oil. Now I'm not sure what to think.

What would you guys do with this engine?

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99 TJ 4.0 5 spd. D30, D44 35 spline chromo ARB, 4.56 gears, 35x12.5x15 Grabbers, eagle alloy 15" rims with 1" wheel spacer, 4.5" RE superflex short arm, 4" currie springs, bilsteins 5100, Rokeman rear coil correction, Taurus Efan w/ DCcontrols Fan controller (FK55), BTF trail cage, skidrow engine/steeringbox/ rad skid, and Super short SYE
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Old 02-09-2014, 03:58 PM   #2
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Did you ever get any word back on this? I'm interested what some others might have to say. I might be replacing my head gasket soon or (I hope not) replacing the head.
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