Question about 1998 Jeep Cherokee

2 Answers

98 jeep cherokee - 4.0 L low oil pressure at idle once warmed up

Oil pressure when first started at 40 - stays there even at edle until 15 - 20 minutes pass - then when at idle dips to the 20 - 25 range - but operates at 40 when driving
what do you think is going on - how serious is it? I am preparing to send the car off with my son to Chicago -

Posted by on

  • dek1957 Feb 21, 2009

    I have a 1998 4.0 XJ 5spd. Runs great! good mileage, everything is
    fine except for this little low knock that is best heard from the front
    seats with the doors closed. The thud (sounds like a rod knock) goes
    away when the engine is first started and the oil pressure goes to
    35+psi. when the engine drops to idle (700-900rpm) the oil pressure
    drops to 5psi and the knock starts and wont stop even if the rpm is
    increased and oil pressure climbs to normal (35+ psi)1000 rpm+. IF I
    shut it back off and restart it and keep the rpm above 1500, there is
    no knock. When I let it idle back down the knock starts in again at
    750-900rpm with 5 psi. One thing i noticed that seemed strange was the
    the pressure would fluctuate 5-14psi at idle with no change in RPM. I'm
    leaning towards a new oil pump, but will get it checked by manual gauge
    first. The spooky thing is the pressure fluctuation and the no knock at
    start up even if I just turn it off and then immediately start it again.
    hummmm? any ideas guys could use the advice.

  • Anonymous Mar 22, 2014

    is this an exhaust manifold problem


2 Answers

  • Level 1:

    An expert who has achieved level 1.


    An expert who has answered 20 questions.


    An expert that has over 10 points.


    An expert whose answer got voted for 2 times.

  • Contributor
  • 33 Answers

The only spec that Jeep gives for the oil pressure is 37lbs @ 1600 rpm. Since you are within specs I would not concern myself with it. Though with a new oil change you will probably notice a slight increase.
Also beware that the 4.0 is known for bad oil pressure switches.
Tell your son to have a safe trip and don't worry.

Posted on Nov 24, 2008

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert who has answered 20 questions.


    An expert that has over 10 points.


    An expert whose answer got voted for 2 times.

  • Expert
  • 86 Answers

It is a serious matter, I advise you to have it checked first before sending it off to chicago. Have your oil pump checked, to explain it to you sir, its like your cars heart is failing.

Posted on Nov 24, 2008

1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

2 Answers

Oil gauge drops low at idle

Low oil pressure at idle can be caused by an engine with worn rod or main bearings due to (usually) high mileage . This however does not mean the engine is still not serviceable as long as the oil pressure is low only at idle. The pressure should at minimum get into the normal range at anything above idle speed.Not much oil pressure is really necessary at LOW speed. At low speed, as long as there is oil getting to the bearings, even at low pressure, you are OK. In a high mileage engine the oil pressure is often low at idle simply because the oil pump is turning slowly and cannot maintain higher pressure between the larger than normal crankshaft and bearing clearances. As speed increases the pump turns faster and supplies more oil and the pressure should go higher. Low pressure as long as it is only at idle is not a problem. However at higher speeds the pressure should be in the normal range. Such a worn engine can benefit from higher viscosity (thicker) oil such as 20W-50 in above freezing weather and 10W-40 in winter. That will increase idle pressure and the thicker oil film maintains a better film between the worn parts

Apr 08, 2012 | 2002 Jeep Grand Cherokee

1 Answer


How many miles are on the engine? Have you tried to replace the oil pressure switch? is the engine making any type of noise due to low pressure reading?

Sep 07, 2011 | 2001 Jeep Grand Cherokee

1 Answer

My 1999 jeep Cherokee 4.0 has a hard time staying on when you first start it. Once it warms up it idles fine.

there is a valve that is located on the exhaust manifold, this controls exhaust flow until the engine is warm if this has gone bad it would explain your problem.

Dec 27, 2010 | 1999 Jeep Cherokee

2 Answers

Low oil pressure after engine warms up in 94 blazer with 4.3

I have a 99 blazer and ever since I have owned it, it reads lower in pressure when idling, but will go up too 40 while driving. This is normal for the vehicle. If the pressure gets real low, and stays low, it means its time for an oil change.

As long as the pressure goes up when you give it gas, it is fine.

Jan 09, 2010 | Chevrolet Blazer Cars & Trucks

2 Answers

2001 Jeep Oil Pressure

Last week my 2001 Grand Cherokee with a 4.7 was dropping below 10 and my "check gauges" light and chime came on. My sending unit was bad. I could see it was bad because oil was getting through the unit and leaking very slow. It's located above the oil filter. Easy fix, but the unit was over $50 and the 1 1/16 special deep socket for sending units was over $10.

Oct 07, 2009 | 2001 Jeep Grand Cherokee

3 Answers

I have oil pressure until i stop , then it drops to below 10 psi

Increase the viscocity of your oil. If you're using 10W30, go to 10W40. If you're using 10W40 switch to 20W50. Don't use single weight oil.

Sep 19, 2009 | 1998 Jeep Wrangler

1 Answer

Low oil pressure reading 1990 jeep cherokee laredo

If this is a high mileage vehicle, say 180k or higher, treatments are not going to help. As mileage increases, the tolerances and clearances in the mating parts increases. This will lower oil pressure. I have a 90 Safari with 192K. Oil pressure was identicle to yours. I put new rod and main bearings in it and now it never goes below 40 psi, even when hot and idling. I tried additives and all I got was more trouble, It started smoking and using a qt. of oil every 300 MILES. I put valve stems seals in and it helped alittle but not near enough. It is now parked and driven only when have to. This is a result of the previous owner of my vehicle not changing oil at regular intervals and overall poor upkeep of it.

Good Luck

Feb 27, 2009 | 2000 Jeep Grand Cherokee

1 Answer

Low oil pressure

the first i would do is to see if the oil sending unit is ok and if you gage is working right and if they are then checkout the oil pump.

Feb 14, 2009 | 2001 Jeep Grand Cherokee

1 Answer

My 98 Jeep Cherokee Sport stays at high idle whenstopping

try checking your vacum hoses could be warn or cracked letting air seep and or could be a faulty choke pulloff

Feb 10, 2009 | 1998 Jeep Cherokee

1 Answer

Low oil psi after driving 25 miles

Have a shop verify the pressure is really low, it could just be the sending unit is defective for the oil press guage, but get it checked, if it really low you could burn out the bearing in your engine, a very costly repair.

Nov 13, 2008 | 1989 Jeep Wrangler

Not finding what you are looking for?
1998 Jeep Cherokee Logo

Related Topics:

1,411 people viewed this question

Ask a Question

Usually answered in minutes!

Top Jeep Experts


Level 3 Expert

74418 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22082 Answers

Jeff Turcotte
Jeff Turcotte

Level 3 Expert

7254 Answers

Are you a Jeep Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides