How difficult is it to change the oil pump on a 2004 Intrepid?

If the noise goes away when the idle speed increases its not the lifters, check the oil pressure is ok at idle and increases with engine speed, check the oil is not to thin or wants changing, the oil pump relief valve may be stuck or the spring spring broken.

First how many miles on the vehicle and how long was the car run low on oil? Most cars today have an integrated fuel pump that will shut off if the engine is low on oil. Most likely you have either gotten some dirt into the lifters causing the noise so I would start with a fresh oil change and filter and add a good oil additive to help clean the insides of the engine. I personally like Rislone products because I have had good luck with them but any good additive that quiets lifters will have a detergent to help clean the lifter and help prevent lifter bleed-down.

It may be the oil pump. If the gauge is going up when the rpms increase it's probably not the gauge or pressure switch. If the computer senses the oil pressure is low it will shut the vehicle off to try to save it's self from catastrophic failure. Also it may start cranking longer before starting. Thats it building oil pressure before the computer will let it start. Make sure oil is full, clean & thick.

Depending on tone and depth of "clicking" it could be anything from lifters to connecting rods or piston pins....

cheapest to expensive:

Replace oil filter

if that doesn't do it (which it doesn't sound like it),

Replace engine...

Because clicking/ticking/clunking noises while having a "low oil pressure" issue (most of the time) means the engine is destroying itself.

it could be a wrist pin, and im not sure if those amc's had hydraulic lifters but sometimes with old lifters when the oil pressure is lower at an idle the lifters arnt filling up all the way so they develope a little valve lash, and when the rpms are raised the oil pressure raises and fills the lifters. you could try chasing the noise down with an automotive stethoscope.

Oil pump is failing. Dont keep driving the vehicle.

One thing you should get checked is the oil pressure.You could have an oil pump that is going out or getting weak.Also depending on how regular you are with your oil changes it is possible that you could have a sticky lifter.The oil pressure at idle should be 4 psi and 25-80 psi at 3k rpm.If it is less than 4 psi at idle do not do the 3k rpm.This is check with a warm engine.(normal operating temp).Hope this helps.Good luck.

lifters taking a minute to pump up. low on oil?

The "lifters" are valve lifter, not oil lifters. They are best described as hydraulic cushions. They use the engine oil pressure to expand and take up the slack between components. As the engine wears, clearances increase and the oil pressure decreases at idle. The ticking goes away with an increase RPM because the oil pressure increases. Using an additive like STP to thicken the oil some might stop it. It isn't uncommon or serious. I had a car once that had lifter noise unless I used Rislone detergent additive to keep varnish from building up around the lifter making it stick. The symtom of coolant in the oil is milkey foam. Some synthetic oils go in clear then turn red or purple. Relax and enjoy the next 100,000 miles. Keep the oil and air filter changed and watch for a leaking water pump. Overheating because the water pump seal or thermostat failed is the death of an older engine. If you want to be proactive, have these and the radiator hoses changed. Avoid a made in China water pump if possible.

A tapping sound could be lifter tick, or rod knock... if it goes away, what you have is lifter tick, check your oil, low oil makes it worse.

Oil pumps up the hydraulic lash adjusters in your valve covers, at lower RPMs, the oil pressure is lower and will not fully pressurize them. Try holding your rpm at about 3500 or so with the car in neutral (parked) and see if it goes away, it should.

In later years (I think starting in 97 or so) mitsu started using a larger bore so called "third gen" lash adjuster. They don't tick as much, but they still do at times.

The good news, lash adjusters are not THAT hard to replace, figure a set of 24 will run you less than 150 in parts.

The better news, it doesn't hurt anything, as long as you can live with the sound, there isn't any reason to change them.

Good luck,
Scott
Iceman_ii on 3si.org