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Old 07-17-2006, 11:31 PM   #1
Join Date: Jul 2006
Posts: 3
Jeep Has Misfire/Poor Performance PLEASE HELP!

Just last week, I decided to put in new U-Joints in the front (Wheel Joints), and a new gear box... All went really well with that stuff...

My 4.0 1994 Jeep Wrangler, 5 Speed, had a leaking rear main, like most, a bad lifter noise (Not running bad though), leaking oil pan, low oil pressure at idle and leaking valve cover gasket

So like most dealer mechanics I believed I could fix anything that came my way... How I wish I worked on more things than just toyota.

I replaced the Rear Main, Oil Pan gasket, Drain plug, Oil Pump (packed it will grease 2nd time around) intake/exhaust gasket, head gasket, and all 12 lifters... in two days, well like 12 hours including beer runs and talking to the girlfriend (big distraction) Hehehe, I really hope she doesn't read this...

All was great for about 2 days, no leaks, no noisy lifter noise, all was great! Yet my oil pressure was still considerably low at idle once the truck warmed up... I was just about to order a soft top for it...

Then I started to hear the lifter noise again, and it started to run like crap misfiring... Oil pressure is low (Around 10 PSI) then once crusing 1500 - 2500 it goes around 30 PSI... When I hear a lifter noise I think thats when it runs like shit... The headers I have run fairly close to the oil pan, maybe warming up the oil making it really thin? I'm going to try different oil filter and thicker oil with an addictive...

Please help me, Bad misfire at times, and low oil pressure, lifter noise ( only comes while driving for a while and then sitting at idle) noise is better than it was but it ran fine untill i replaced them... How can I raise oil pressure? I know a motor might be in the picture but i rather not...

It also has new plugs, wires, cap rotor... all the good stuff... no vaccum leaks and compression seems to be good.... my exhaust has a fair share of new leaks but i don't think it would cause it to missfire, even with the 02 sensor the way it is... Please any help suggestions or comments will be help ful...

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Old 07-19-2006, 01:36 AM   #2
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Join Date: Aug 2005
Location: upstate ny
Posts: 119
sounds like bad mains making the oil pressure drop till the revs come up if the mileage is near or over 200k i would say a new motor is in need or a new crank and a rebuild

95 yj 4.0 4 inch bds and 1.5 shackle lift 33inch swampers for summer and 32 inch mudkings for winter 8500# milemarker winch and homemade high lift / light mount on hood

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Old 07-27-2006, 05:39 PM   #3
Join Date: Jul 2006
Posts: 3
Well its been a while but I figured it out after the motor was making a terrible noise one day...

After working on brand new cars all day I got into my rough jeep, and knock knock knock the motor went... So I drove it home and waited for it to blow up...

Took the valve cover off started it and noticed the 5th cylinder exhaust valve wasn't hitting at all...

took the rocker arm assemby off and started it, sounded great except for the miss...

used a pushrod to feel the lifters, intake hard as a rock (good), exhaust nothing... bad... off the head comes again...

well about 5 hrs later and 50 bucks for a new head gasket oil valve cover and lifter it was purring like a little kitten...

its been 2 days and 100 miles later still good...

the lifter i pulled out was shot, whole in the bottom of it, hopefully just a bad part... the other lifters looked to be ok, and so did the cam... I don't think oil pressure has anything to do with the issue I had, becuase 6 cylinders do get low oil pressure 13 psi at idle and more while crusin. Which mine does...

thanks for your help....
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