Misfire on slight throttle

AC has nothing to misfires or o2 sensors.

Start with the basics.

Check the spark plugs, or perhaps just replace them all. Or you can test, put plug 5 in plug 1 swap. Does the misfire move? If it does, the plug is the issue, if it doesn't is is the coil pack to it.

Clean throttle body and MAF.

Clean EGR

Run car for a week, and if it is still running rich, change the sensors.

OR, just go to an auto-electrician with a $5,000 scan tool computer although with a 1999, the data will be fairly basic but will diagnose.

https://www.google.com/search?q=1999+Lincoln+Town+Car+shakes+at+idle.+Cylinder+5+misfire+and+bank+1+and+2+too+rich

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Definition of Diagnostic Trouble Code P1506 Audi: Closed Throttle Position Switch Does Not Open/Short to Ground BMW: Idle-Speed Control Valve Opening Solenoid Control Circuit Signal High Ford: Idle Air Control Overspeed Error (see P0507) Jaguar: Idle Air Control System RPM Lower Than Expected - B Bank Kia: IAC Valve Opening Coil Voltage High Lincoln: Idle Air Control Overspeed Error (see P0507) Mazda: Idle Air Control Overspeed Error Mercury: Idle Air Control Overspeed Error (see P0507) Porsche: Throttle Jacking Unit Lower Mechanical Stop, Signal Implausible Volkswagen: Closed Throttle Position Switch Does Not Open/Short to Ground Volvo: IAC Valve Opening Signal
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Definition of Diagnostic Trouble Code P1151 Audi: Bank1, Long Term Fuel Trim, Range 1 Leanness Lower Limit Exceeded BMW: Oxygen Sensor Heater Circuit Signal Intermittent (Bank 2 Sensor 1) Ford: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Jaguar: Lack of H02S-21 switch, sensor indicates lean Land Rover: Lambda control limit bank 2.Implausible signal/condition Lincoln: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Mazda: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Mercury: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Subaru: HO2S-12 Heater Circuit High Input Toyota: Coolant Path Clog Up for Coolant Heat Storage System Volkswagen: Bank1, Long Term Fuel Trim, Range 1 Leanness Lower Limit Exceeded
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Definition of Diagnostic Trouble Code P0302 Category: Powertrain Definition: Cylinder 2 Misfire DetectedNote: This definition of P0302 is applied to all manufacturers
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Definition of Diagnostic Trouble Code P0171 Category: Powertrain Definition: System Too Lean Bank 1Note: This definition of P0171 is applied to all manufacturers

This is the diagram for the 4.6 1998 Ford Expedition.( Notice the numbers 1-2-3-4 spark plugs are on the left side if you are facing the front of the vehicle.) Please rate my answer if you were helped.
Thanks

P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)
P0301 Cylinder #1 Misfire Detected
P0302 Cylinder #2 Misfire Detected
P0304 Cylinder #4 Misfire Detected
P0306 Cylinder #6 Misfire Detected

OK, We'll cover the Diagnostic Test Codes (DTCs), starting with the standard definition set by SAE J2012 (Revised December 2007)
DTC P0171 "System Too Lean Bank 1"
DTC P0174 "System Too Lean Bank 2"
DTC P0301 "Cylinder 1 Misfire Detected"
DTC P0305 "Cylinder 5 Misfire Detected"
DTC P0316 "Engine Misfire Detected on Startup (First 1000 Revolutions)"

The "system lean" codes are pretty much telling you that there is way too much oxygen in the exhaust. There is too much oxygen on BOTH sides of the engine, and that is why you are getting codes for bank 1 and for bank 2. Bank 1 is the side where #1 cykinder is located and Bank 2 is the opposite side.

The misfire codes are pretty self-explanatory. #1 and # 5 cylinders are misfiring. The P0316 DTC is telling you that the misfire monitor is detecting a misfire as soon as the engine starts. This tells you that it is a very severe misfire and that the engine does not have to warm up and the car does not have to be driven to detect the misfire.

A misfire can be caused by many things it can be vacuum leaks, bad spark plugs, bad ignition cables, faulty ignition coils, fouled or malfunctioning injectors or injector circuits, blown head gasket, cracked cylinder head, burnt valves, etc.. etc..

However, look at the codes you have. Then look at the firing order for your engine. 2002 Mercury Sable is only equipped with a 3.0L 2V 6-cylinder engine.
The firing order is 1-4-2-5-3-6

Now if you take the firing order and split it in half, stack the two halves on top of each other, it looks like this:
1-4-2
5-3-6

When you look at the firing order this way, you can see that cylinders 1 an 5, 4 and 3, and 2 and 6, are "PAIRED" cylinders. They are exacly opposite in the firing order. Now, the cylinder only fires every second revolution of the crankshaft. With paired cylinders, one of the cylinders in the pair will fire on the first revolution and the other cylinder will fire on the second revolution.

Looking back at your codes, please note that the cylinders that are setting the misfire codes are paired cylinders.

Now the coil pack for your ignition is actually made up of three coils. Each coil fires a set of paired cylinders. If you look at the top of the coil, it will usually be marked with the cylinder numbers that each coil tower is supposed to connect to. The coil will look just like the firing order split and stacked as above.

With all of this said, I would say that it is VERY LIKELY that your misfire codes are being caused by a defective ignition coil.

The lean codes are a little different.

These are USUALLY caused by vacuum leaks which allow too much air into the engine that is not getting measured by the Mass Airflow (MAF) sensor and causes the engine to be getting too much air and not enough fuel (running lean).

I would take a good look at all of the vacuum hoses and lines. Ford is notorious for getting holes in the rubber parts that connect the PCV tubes.

If you do not find any obvious reasons for a vacuum leak, then you may want to fix the misfire codes, reset the computer memory, and drive the vehicle to see if the lean codes come back again. The misfires COULD be the cause of the lean codes. In a perfect world, this is not supposed to happen because the misfire monitors setting codes will not allow the oxygen sensor monitors to run and set lean codes. However, I HAVE seen cylinder misfires that have caused lean codes.

I hope this helps you to figure it out. Good luck!

P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure

It means that your engine is running lean - not getting enough fuel for the amount of air that the engine is receiving. Because your maxima is equipped with a V-6 engine, whatever the problem, it is affecting only bank #1. Bank #1 is always the side of the engine where cylinder #1 is located, or in your case, the left side of the engine as it is viewed while facing the crankshaft end of the engine.
(on a 4 cylinder engine, there is only one bank and it is always referred to as Bank #1)
There are several things that can cause a lean condition including vacuum leaks, a malfunctioning Evaporative Emissions system, a misfiring cylinder (due to bad plugs, bad injectors, or an intake or head gasket leak.), a malfunctioning Mass Airflow sensor (MAF) or Manifold Absolute Pressure sensor (MAP) or even a bad Oxygen sensor (O2s) (Nissan sometimes calls an O2s an "Air-Fuel Ratio Sensor") It is even possible for a leaking vacuum brake booster to cause a lean code.
If there are any other malfunction codes present, it may help to pinpiont the cause of the lean code. (Like a P0301 "cylinder#1 misfire detected", in which case, you would address the misfire code first.)
Certain problems, like a leaking brake booster or a bad MAF will usually set lean codes for BOTH banks.
If the P0171 is the ONLY code present, the most likely cause is a bad O2s, but I recommend some diagnostic testing to prove it before spending the mega-bucks that Nissan gets for their O2 sensors.

take sample of your fuel into clear plastic bottle from fuel line
is there any water present?
this can cause these codes and then not go on storing codes for other bank even though that bank will be missfiring also due to water & P0300 Random/Multiple Cylinder Misfire Detected being logged
check all connections to coils/leads & wiring connectors
due to miss fire codes for cyl 1,3,5 all on the same bank
also look and check for air leaks on that bank (hose knocked off or splithose)inlet manifold gasket,brake booster etc...
3 injectors being blocked slightly on same bank posible!!!
check wires and signal

was it running like this b4 tune up & repairs?
this is what codes are
P0170 Fuel Trim Malfunction (Bank 1)
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0305 Cylinder 5 Misfire Detected

the last code is for trans due to misfire/running lean on bank 1 probably a torque problem code

1. P0171: This means that the oxygen sensor has detected a lean air-fuel ratio. This can be caused due to a vaccuum leak or a problem in the HO2S circuit or the HO2S (Heated Oxygen Sensor) itself. (Bank one Sensor one). This is commonly located along the exhaust pipe. It could also be a bad Mass Air Flow sensor or a bad Engine Coolant Temperature sensor. Diagnostic checks will be needed to be carried out to be verified though
2. Well as for the other codes, it means #3&4 cylinders are misfiring. It is a possibility that the P0171 code mite have caused the others to show up. I can be wrong though. But it is a strong possibility. If the air fuel mixtue is too lean indeed, mis-firing will occur, unless it is an actual electronic and not a mechnical problem. By the way, when these codes appear, how is the engine's performance. Does it remain the same or behaves poorly?

complete tune up plugs wires distributoe cap and rotor