I have a 2000 Pontiac Firebird with 90,000 miles on it. I put in Gunk engine cleaner and ran it for 5 minutes as directed then drained the oil. I then did an oil change (Quaker State 10-30) and put in Lucas oil stabilzer (heavy duty). The oil pressure at idle is 90 psi and when driving it could go as high as 110 psi. I removed the oil pressure sensor and blew it out with compressed air and there was no change. If the sensor is faulty would it show high pressure? Do I have oil blockage or is the Lucas oil creating temporary high pressure.

Try spraying carb cleaner in throttle body , see if starts ! Do you have a security light on the dash ? How many miles on it ? And is the spark happening at the right time ? jumped time , timing chain !

I would say it is the oil pump failing or worn main bearings on the crankshaft.

check engine on? if so have a diagnostic run on it .

If your oil level is good, when I say good I mean between the full and low marks. This could be a faulty sensor, a bad oil pump or a partial blockage some place. Try changing the oil and filter. When you do so, get a can of GUNK Engine cleaner it is an oil additive you put in before you drain the oil. You add the Gunk cleaner to your oil, run the Engine for 5 minutes and then drain the oil. Do not run the engine for more than 5 minutes with this cleaner in the engine or it could cause damage. A lot of people recommend using SeaFoam to do this but this is your choice. The GUNK is cheaper in most cases. After running the motor for 5 minutes Drain the oil and change the filter, Add new oil of the proper type for your vehicle and see if it resolves the problem. For your vehicle it is most likely using 5W20 and should take 4 to 5 quarts if you change the filter and oil. You may want to consider using SLICK50 and 3 to 4 quarts of oil instead of straight oil because of the age of the vehicle. I do recommend this. I have never had an Engine seize after using slick50 at an oil change. If this doesn't correct the problem, you can try replacing the oil sensor but that typically will show you a fault code. With no fault code from a check Engine light and having done all of the above, I would look at replacing the oil pump but again, this is your choice.

The oil pump screen should even be visible to you unless you are removing the oil pan. It only blocks fairly large debris and if you have that problem you have a much larger problem somwhere. If you suspect build up is a problem try running Gunk Engine cleaner before your next oil change. Make sure you follow the directions. It' s an actual additive you add to the engine before an oil change. Run the engine 5 minutes, no more. Then drain, oil replace filter and refill. If your having oil pressure problems there is something else wrong though as this is very difficult to clog unless you have broken something in the engine.

if your saying you suspect sludge then you may have an oil passage clogged. Trying to use cleaners can actually worsen the condition if the passage was partially clogged and you broke a piece of the sludge off. Not serviceing the oil enough is the cause of the sludge if its got to that point.

your oil pump does that on purpose - more noticeable with a dented oilpan as pressure is slightly increased. nothing to do until it goes (if it goes) unless you want to throw parts at your car anyways.

look for a melted wire loom you have or a pluged fuel filter

Probably didn't hurt it, my 2002 was ran for 2000 miles 1 1/2 quarts low on oil due to dummies putting only 5 quarts of oil back in it after changing the oil. It takes 6 1/2 quarts. It didn't hurt it at all.

Normal Maintenance Details
90,000 Miles (144,000 Kilometers) : All Applicable Models
PERFORMED OPERATION COMPONENT
INSPECT BALL JOINTS
If equipped.
INSPECT BRAKE SYSTEM
Inspect brake pads, shoes, rotors, drums, brake lines & hoses.
INSPECT COOLING SYSTEM HOSES & CLAMPS
INSPECT DISC BRAKE PADS & ROTORS
INSPECT DRIVESHAFT
If equipped.
INSPECT DRIVESHAFT/PROPELLER SHAFT U JOINTS
INSPECT EXHAUST SYSTEM AND HEAT SHIELDS
INSPECT PARKING BRAKE SYSTEM
INSPECT STEERING LINKAGE
INSPECT SUSPENSION COMPONENTS
LUBRICATE DRIVESHAFT/PROPELLER SHAFT U JOINTS
LUBRICATE STEERING LINKAGE
REPLACE AIR CLEANER/ELEMENT
REPLACE AUTOMATIC TRANSMISSION FLUID
REPLACE CABIN AIR FILTER
If equipped.
REPLACE CLIMATE-CONTROLLED SEAT FILTERS
If equipped.
REPLACE ENGINE OIL
REPLACE ENGINE OIL FILTER
REPLACE FUEL FILTER
ROTATE TIRES
90,000 Miles (144,000 Kilometers) : RWD
PERFORMED OPERATION COMPONENT
LUBRICATE BALL JOINTS
2000 Lincoln Navigator
Maintenance
...sorry if not too readable