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Discussion Starter #1
Hi All
New to the forum, but been a lurker for awhile.
My '97 2.7L 4X4 just turned 150K. Had a slight miss for months, but never thought much of it. Just recently got the CEL with 300 and 301. Changed out plugs, wires, and both coils.... no change. Started to intermittently idle rough a week or so ago, finally checked the compression (120psi in the #1, 165 #2-4). Runs OK one day, rough idle the next. Codes bounce back and forth 300 one time, and 301 the next... sometimes both back to back, (sometimes nothing for a couple days). Last couple days the dreaded blinking CEL.... Could my real problem be a bad injector in the #1 (or other fuel related prob), or is this the norm with a weak hole? I don't want to do a valve job and end up burning a valve again before I can diagnose the real cause.... Any feedback would be appreciated.
Jeff
 

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Sounds to me like you need to do a valve clearance check.. my $$$$ is on a valve job if the exhaust is out of spec, it sounds like to to me your already about 25% off from # 2 ~4 for #1. Pretty common on those motors
 

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Discussion Starter #4
Thanks for the feedback guys.
Pressurized the #1 cylinder to find out where the leakge is. I hear some air coming out the tailpipe, and some coming out around the spark plug opening in the valve cover (but not out the oil filler cap location). Compared the test results with the #4, no leakage anywhere. Probably an exhaust valve, but the air leakage around the plug opening has me baffled.... valve guide maybe, but no oil usage or blowby.....? I'll pull the valve cover off and check clearances next.
 

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Discussion Starter #5
Follow up-
Pulled the valve cover and adjusted the valves, as the clearances were down to virtually nothing on the ex valves. No more CEL, runs like it is supposed to as far as I am concerned for over a week now. Rechecked the #1 hole today to see if the compression came back up on that weak hole. Unfortunately it is now down to 80psi (can't believe how good it idles like this). Could have burned the valve further since the last comp test before valve adj, or it is just continuing to burn further now that it has already begun to leak... Guess I'm going to be pulling the head after all. At least it gave me the chance to verify that it was not a fuel related problem. Thanks for the help.
J
 

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If your valve clearances were at 0 it sounds like you already burnt a valve, Remove the head and I bet its already burnt.
 
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