2.5 four cylinder low oil pressure... fix - JeepForum.com
 
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post #1 of 5 Old 12-02-2010, 12:03 AM Thread Starter
wubbaldo
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1997 TJ Wrangler 
 
Join Date: Nov 2005
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2.5 four cylinder low oil pressure... fix

One day on my way to work the oil pressure suddenly dropped to near zero . I caught it and pulled over. When racing the engine it would climb back to over 30 psi on the guage. Mileage on engine at that time was about 92000. I let it idle to see if indeed the pressure was far enough down to let things begin to starve for oil. The lifters were as quiet as new, so I knew that there was not a oil pressure problem. I replaced the oil pressure sending unit and peptobismol the pressure was back to normal readings. The pressure sending unit on a 97 tj is on the passangers side about next to the distributor, yes it has a distributor. The sending unit is expensive and requires a deep well socket to remove and install.

I noticed last summer (about two years after replacing the sending unit) that using 5-20 oil the pressure does indeed go down to below 40 but never below 30 psi as shown on the instrument cluster. This made me curious so I installed a NAPA GOLD oil filter and my pressures never goes below 35 at idle with engine hot and normally hangs about 45-50 psi. Wierd how a different brand of filter would make that diffference. I was using ValvolXXX filters but now use the NAPA Golds exclusively.
To see if I had a fluke filter I changed back to a ValvoXXX and started the engine and kept it at idle speed for 2 minutes no foot pedal at all. The pressure was at 28 psi. I was checking the pressure at the engine not the guage using a mechanical guage hooked up to the pressure unit location.
I then changed the filter to a Napa Gold and started it up again not changing the oil. The pressure at idle speed for 2 minutes was 41 psi.

Enough said.

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post #2 of 5 Old 12-02-2010, 12:12 AM
odinseye84
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An important lesson---depending on where the pressure is measured, a higher oil pressure reading could actually mean a more restrictive oil filter.

The likely reason 5w20 has "less" oil pressure is because its flowing better, and the sensor gauges less backpressure. Flow is important.

Some of the more expensive, premium filters have been labeled more restrictive due to better filtering or synthetic media, or just too many pleats stuffed in there.

Reminds me when i worked at a dealer and one of the oil change monkeys was bragging about how he put in some 40 weight oil and had "better oil pressure".... which was likely just more restriction!
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post #3 of 5 Old 12-02-2010, 04:59 PM Thread Starter
wubbaldo
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Yes I agree

Thanks for your comments:
In the summer I use Castrol 20-50 and never see a pressure under 38 psi.
I change back in the winter (live in Montana) to thinner oils for ease of starting.

I just wanted to let folks know that there are different oil filters out there and if they are willing give it a try sometimes.

I hooked the mechanical guage to the oil pressure sending unit location to test the pressure at that spot. I'm not sure if the oil goes to the block channels before it goes through the filter. When I disassemble the motor if that was ever happens then I'll take note of the casting passage ways to see if that indeed comes right from the oil pump.

Thanks again
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post #4 of 5 Old 12-02-2010, 05:19 PM
odinseye84
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Also think about this--- when your car sits out all night in the cold temps, the oil pressure is very high due to the oil being very thick-- restriction.

That being said... i still use a purolator pure one filter which is criticized for being very restrictive! Im sure it still flows plenty for the motor...


valvoline filters might be made by fram, i cant remember.
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post #5 of 5 Old 12-02-2010, 05:30 PM Thread Starter
wubbaldo
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Join Date: Nov 2005
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Response to reprogramming the PCM Adaptive Memory

There is a post on this already. Look for reprogram the computer in the search. The original article was posted by MarkG on Thursday, April 15, 2004 from Chrysler products division.

The reason I was bringing it up was that I changed the plugs and wires at 100000 miles and reset the computer to relearn the new engine conditions. I thought this would help with fuel economy etc..

I also reprogrammed the computer after I installed a throttle spacer, yeah I know on a 4 cylinder?.. Yes on a 4 cylinder.

I then reprogrammed again when I replaced the header using a Pace setter header ceramic coated when the old one cracked. Pacesetter was the only one available at the time I was looking. If I had my druthers I would rather use someone elses header as the pace setters output discharge tube (exhaust pipe not header pipe) does sit a bit lower than the factory one. Could be a chance for a rock and header pipe to get too close for comfort. As is sits it is working extremely well so far. No I did not put a loud muffler on it. I am a video-ographer and I want my machines very very quiet....

PS after all the reprogramming I cannot get the Jeep to have the acceleration and pull power that the dealer did when I purchased it. I had the dealer tune it a bit when I first got it and there was a remarkable difference in pulling power.

By reprogramming the computer adaptive memory I cannot duplicate the dealers efforts.

Mine with a 4" lift yeilding 5" since it is a 4 cyl and has no weight and running 31x10.5 Traxis tires and 4:56 gearing gets around town 20.5 in the winter to 22 in the summer months. I think I'm lucky..

Thanks for the read, this is way better than Face Plant....

Last edited by wubbaldo; 12-02-2010 at 05:37 PM. Reason: spelling errors- added credit where it was due.
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