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Rsteven 10-12-2009 12:34 PM

Need help!
I recently took a TJ in on a swap and it has recently developed a problem. It is a 2000 TJ Sport with Auto and 4.0, 31 x10.50s with 89000 miles. Skyjacker 4" lift. After bringing it home 10 miles I swapped all the fluids, engine oil, filters, serviced transmission, differentials, transfer case etc. took it on a test drive and noticed oil pressure dropped to about 10-12 at idle from 40 cold. No problem, until it idles after really warmed up, then drops to 0 on the gauge and stays there until idled up. Just changed the oil pressure sending unit and it does the same thing. Motor sounds great, runs great no noises that are unpleasant. I will try to purchase a mechanical gauge and try that next. Could it be the gauge in the dash? I did notice the oil pressure was low at idle before I changed oil (10w30 GTX) , but didn't notice it zero out.

mudslinger150 10-12-2009 12:38 PM

some do that if im not mistaken... someone? Mine will fluctuate with rpms some of the time

woods453 10-12-2009 03:53 PM

Fluctuate yes, but not to zero on mine. There are no leaks?? Can you smell oil?

BlackArmada 10-12-2009 08:23 PM

mine used to do that, i ended up with an engine full of water and antifreeze.

Nitemaher 10-12-2009 09:34 PM

New to this site but not to engines. What oil filter brand did you put on ? It could have colasped Fram HPs have this problem at times. Your idea on the mech guage is a ture answer for trouble shooting.

Rsteven 10-13-2009 04:48 AM

Thanks for the suggestions, I appreciate all your comments. The engine seems to sound and run like new, no smells, no noises. It holds about 10 psi on the gauge at idle when completely warmed, and then drops to 0 quickly and stays there. While their you can blip the throttle, no noises, no smoke, and then the pressure goes up to about 15-20. Then it returns to 10, holds there for a moment, then drops to near 0. I understand oil pressure fluctuates, I just need to know if something bad is about to happen. The only other problem the sport has is twice now, I have shut it off after warm, actually hot here in central florida, and when I restart it it runs like sh%#t for a short time, misfires a bit then smooths out as if nothing happened. Fresh spark plugs when changed fluids, old plugs were perfect in color. Oh the fun.. Thanks again for the help. Oh and it was regular 10w30 Castrol GTX with a premium oil filter.

crazyredneck 10-13-2009 12:01 PM

mine will run like shit after i get off of the highway and get into town and go inside somewhere, come back out fire it up and like you said it runs like shit. but normally only when it is 90+ outside.

it actually because the fuel in the fuel rail evaporates (boils), there is no air flow under the hood when the motor is off so the heat just builds up off of the exhaust headers and the fuel rail is above that and the intake manifold.

chrispy42 10-13-2009 06:31 PM

oil gauge dropping while stopped
i have exact same problem, stays fine while driving but when I stop will drop to about 10 and some cases zero. been told by several mechanics to replace oil pick up tube...

Rsteven 10-14-2009 04:17 AM

Thanks for the help, the engine problem is when the tempertures have been 90 plus, and the hesitation and stumbling goes away momentarily after starting. Sounds like this symptom with the oil pressure is fairly common, I will let everyone know what happens as I work it out. You are correct about the heat under the engine, it gets so hot you can't grab the hood prop without "feeling the heat under the hood"

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