I've trolled the forum for a while but didn't sign up on this board until recently when i purchased my 98 xj with 150,000 on the clock. Green classic with very little rust, for a northern Illinois Jeep. RC 4.5 lift with 33 M/T claws, and some poo-pipe tube bumpers and BRAND NEW HEAD. It had been sitting for roughly 4 years untouched. I got a great deal on it and couldn't say no. Obviously it didn't run after sitting 4-5 years, the gas tank was GROSS, so I cleaned it out, threw a fuel pump at it, changed fluids, added about 5 gallons of gas and it fired right up and ran OK but loud, ticky, and diesel sounding. Also owning a TJ, I'm well aware some noise is to be expected, but this seemed excessively noisy. As the weather started warming up i tinkered with it installing new plugs, wires, cap and rotor, along with PrecisionInjectors ev6 kit. Eventually i noticed, it running rough but no check engine lights. The old school "squirt some water on the exhaust manifold" trick confirmed #1 and #6 were goofy. sometimes i could start it and all 6 would fire. Sometimes either #1 or #6 or both would fail to fire. I researched all of the sensor tests via google advaced search on this board as well as some other jeep forums. Cleaned and greased the NSS(I didn't expect this to help, did it more as a preventative measure) tested the crank sensor, tested OK. replaced the throttle sensor, had a spare in my toolbox. At this point, I was confused because i could verify spark and fuel were present, plus sometimes, #1 and #6 would fire, and other times not. This morning i ran to the parts store and rented a compression gauge. #1 20 #2 155 #3 160 #4 155 #5 165 #6 95...weird. thought about it over lunch, trying to figure out how to tell my wife, it may need....rings, valve job, head, head gasket... i decided to remain silent and delay the discussion. after lunch i pulled the valve cover and............

Every single rocker bolt was LOOSE were talking backed out 4 or 5 threads and easily tuned by hand, and all 12 of them. Only one bolt was snug and i was able to twist it without the ratchet(likely pressure on it from the cam). I also want to note, the valve cover had a few knicks and tiny dents from push-rods bouncing out, or rocker arms whacking it, not sure. I looked up the torque specs and found 21lbs to be the correct. This isn't much, and i didn't want them coming out again, so i torqued them all the 30 with a TINY dab of light lock-tite. Buttoned everything back up and compression test now showed about 135 on #1 and 145 on #6. When i cranked it, she started easily and immediately. Also notably quieter than previously, and also quieter than my TJ.

I'm assuming the PO, who put the new head on, just forgot to tighten the rocker arms. I've worked on tons of cars for years in my free time, and consider myself a pretty decent hobby mechanic. Ive never seen this and I'm so glad i looked at them and figured it out before something BAD happened...

I wish i took pictures, but i didn't. May pull it back apart next Saturday and make sure none of the push-rods bent. Anybody seen this before? jeep or any other car? Also, how worried about the low compression on cyl #1 should i be? im figuring it might need rings... the head is obviously brand new, unless the PO cleaned it REALLY well prior to sale while leaving the rest of the engine bay untouched....

Please don't bash too bad on first real post.

 

Also i don't understand the increase in compression with rockers tightened down properly. loose rockers should mean valves stay closed, so there should be compression...? am i wrong?

 

If the intake valve isn't opening how are you supposed to get air into the cylinder to compress? Understand now?

 

yerp, but nothing leaves either with exhaust closed right? unless all that air passes the rings. I do get your point, just peculiar...

 

Obviously just a weird combination of some rocker arms just tight enough to open and close enough to allow air flow.

 

I'm thinking I should check mine, my engine seems awfully noisy lately.