P0304 P0300 Leak-down and compression test results - JeepForum.com
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Unread 02-05-2014, 01:24 AM   #1
NizmoTJ
Registered User
1999 TJ Wrangler 
 
Join Date: Feb 2012
Location: Las Vegas, Nevada
Posts: 34
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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