pimpinr

01 jeep XJ, when i idle at a red light or when i turn on the car it shakes until i push the accelerator.. Oil pressure gauge goes down when im slowing down or am completely stoped and goes up as i move.. My jeep has 175xxx and uses pz 5w30.. Could that be the issue? I will change the oil sending unit this weekend

salad

What RPM is this thing running when it shakes?

Oil pressure sending unit could be faulty, yes. What kind of pressure do you have when driving around?

Have you ever had to top up the coolant?

md21722

The fact that is starts shaking is a bigger problem than the oil pressure gauge. It could be a faulty sensor or dirty idle air controller causing a near stall condition. Are there any codes? It is a good idea to check with a mechanical gauge on the oil.

tjwalker

The fact that the oil pressure goes up and down with rpm is normal. Here are the oil pressure specs for the 4.0. If you are within these limits, you're fine.

*Not less than 13 psi at HOT idle
*Between 37-75 psi over 1600 rpms

The symptom of wanting to stall at idle is a separate one. Have you ever seen a check engine light? If so, you must retrieve codes from the computer for clues/guidance. In the absence of any codes, I would recommend you perform the procedure I'll detail below. Good luck and keep us updated!
----------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

pimpinr

Update.. It was the oil sending unit, and also changed the throttle position sensor and my rough starts decreased a bit. I am now getting error code p0301..