my 2003 jeep liberty sport has a misfire running very rough why? on 2003 Jeep Liberty

check engine light was flashing replaced all coils checked all injectors (all firing) replaced computer (brain) check engine light went off. still misfiring compretion test numbers were between 125 and 140 except one cyl was at 25 pulled passenger side valve cover. valve rocker had fallen out now the hydrylic lifter wont seem to hold rocker in place got it to stay in place for a short period of time (very short period of time) but ran well for that short amout of time before it fell back out why wont the rocker stay in place? lifter was pumping oil out so figured it would have enough oil pressure to hold it in place please help. thanks

by in Saint Petersburg, FL on January 12, 2014
1 answer 8 comments
ANSWER by on January 12, 2014
Check valve stem height, very possible 'that' valve seat in the head has dropped down out of the head. It will intermittently pop back in place and with the rocker installed it WILL run ok for just a few cycles until it drops down again holding the valve down then the rocker jumps off again. ("IF the valve and seat were ok, so should be compression"!!!) Head will have to be removed to fix!! Has the engine ever overheated? Need to know that as well.
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COMMENT by on January 12, 2014
ok thank u for your reply I will check valve stem height (does head need to be removed to check valve stem height)? as far as I know it has never overheated but im not to sure just bought it not to long ago thought it wouldn't be this serious but such is my luck. ive had it running (idleing not driving) for pretty long periods of time and temp gauge has never gone above half way. I have been told if I need to macheine the heads and top half of engine to fix it will put to much strain on lower half and probably should have the whole engine rebuilt instead?
COMMENT by on January 12, 2014
With the cam lobe up on the valve next to this one are both valves the same height with that one rocker removed? Should be,, but if the seat has popped back in place it is hard to tell. As far as what you have been told well.... How many miles on the engine?
COMMENT by on January 12, 2014
ok thanks so much I will try to take a look at the stem heights. By the naked eye that valve and the one next to it look to be at the same height the engine has 152000 miles on it
COMMENT by on January 12, 2014
When you checked compression, were both valves working, rocker back in place? Can you tell me if the defective valve is the exhaust valve?
COMMENT by on January 12, 2014
when compression was checked the rocker was not in place because the valve cover was still on and I didn't know rocker had dislodged itself till after I took valve cover off as far as the valve being the exhaust valve im not sure its the valve closest to the firewall on passenger side on a 3.7 jeep power tech 2003 if that helps
COMMENT by on January 12, 2014
That's the exhaust, just wanted to be sure because it has got to INTAKE air to have compression!! And it was since the int valve was working. The bigger 4.7 V/8's do this same thing, same valve!!! Check around and see what is the best direction for you to go in. It's not going to be cheap either path you take, sorry. Have a MECHANIC check it out just to be sure. Good luck with it.
COMMENT by on January 12, 2014
thank u so much for ur information and time thanks again
COMMENT by on January 12, 2014
Sure, wish i could have had better news!