Wrangler TJ 4.0 - Oil Pressure 30 PSI at 4,000 RPMs? - JeepForum.com
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post #1 of 3 Old 07-12-2019, 09:17 PM Thread Starter
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Wrangler TJ 4.0 - Oil Pressure 30 PSI at 4,000 RPMs?

Hey guys,

2004 Wrangler, 4.0 inline 6 cyl. 140k miles.

I've been having the infamous oil pressure bounce to zero when idling after the engine warms up. I tried an oil sensor swap and that didn't help. Took in to mechanic, whom hooked up a gauge and said it idles at 8-9 psi, and is only at 30 psi when reaching 4,000 RPMs. From what I've read it should be 10 per 1,000... he said confidently that the engine needs rebuild. Is he right? Is 30 psi that bad? Should I try another sensor?

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post #2 of 3 Old 07-12-2019, 09:29 PM
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2000 TJ Wrangler 
Join Date: Oct 2010
Location: Clyde
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If the mechanic hooked up a mechanical pressure gauge and it read what you state, replacing the electronic pressure sensor isn't going to change a thing. You can try a different oil filter hoping that maybe what you have is too restrictive (Wix is a very good choice), or consider replacing the oil pump hoping that the old one is worn, but chances are good the root cause of your oil pressure problem will be worn cam and crankshaft bearings.

Normal spec for oil pressure on the 4.0L is a minimum of 13psi at idle, and 37-75psi at 1600rpm and higher.
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2000 TJ SE
2005 LJ Rubicon
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post #3 of 3 Old 07-12-2019, 09:57 PM
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2003 TJ Wrangler 
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If you haven't figured it out yet, your dash gauge is a fake. The sending unit is just an on/off switch. So the gauge will always read the same until you've got no pressure at all. I recently checked my bearings while doing a rear main seal and found 2 totally wasted/almost spun bearings. The fake 2003 gauge was reading above 1/2. New bearings, oil pump, and a real gauge now the pressure is 68-72 going down the highway, 37 @ hot idle.
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