2003 grand marquis with misfire code p0316

If you changed the #5 Coil then the code was wrong

You get lots of wrong codes on a ford, as a bad coil
spikes the pcm when grounding out to fire the coils
secondary side

Try putting the old coil back & walking the new one to
another cylinder,may take many days & many miles of
driving to get it fix,but better than a shop guessing, because
they hate fords

Okay, you were getting code P0306, and a P0316. You have replaced plugs and swapped coils around are you still getting the code P0306? or is it a different code for a different cylinder now? Replacing your crankshaft position sensor in this case will merely waste your money. Its doing its job, the P0316 is telling you you had a misfire in the first 1000 revolutions of your engine at startup, the P0306 is telling you its probably cylinder #6 that had the problem. there is no code there indicating your CKP is bad.

Now if you swapped your coils and the misfire is still on cylinder 6, its either injector problem, or base engine. If the misfire has moved to another cylinder, replace that COP.

Hope helps.

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!

Cauases or fault codes are not cut and dry, but here are the possible causes of codes P0316 and P0306 which are related codes.
P0316 - Engine Misfire Detected on Startup
Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Engine fails to start
- Engine runs rough Possible causes - Crankshaft Position (CKP) sensor harness is open or shorted
- Crankshaft Position (CKP) sensor circuit poor electrical connection
- Faulty Crankshaft Position (CKP)
- Ignition System
- Fuel Injectors
- Running out of fuel
- Fuel Quality
- Faulty Engine Control Module (ECM) P0306 - Cylinder 6 Misfire Detected Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Lack/loss of power
- Hard start
- Engine hesitation
Possible causes - Faulty spark plug 6
- Faulty ignition coil 6
- Ignition coil 6 harness is open or shorted
- Ignition coil 6 poor electrical connection
- Clogged or faulty fuel injector 6
- Injector 6 harness is open or shorted
- Injector 6 poor electrical connection
- Improper spark plug 6
- Insufficient cylinder 6 compression
- Incorrect fuel pressure
- Intake air leak

Hi

P0305 is misfire in cylinder #5.
P0306 is misfire in cylinder#6.
P0316 is misfire on start up.
Have the plugs on those 2 cylinders, and the 2 fuel injectors checked, also check for spark from the coil on those 2 plug wires.

Please get back to us if you have further query or else please accept the solution.

Thanks for contacting fixya.com

You have a misfire on #3 for code p0303 & misfire for code p0316

P0306 is cylinder 6 misfire..P0316 is misfire in the first 1000 revolutions. A proper tune up will probably take care of the code. This includes spark plugs. I have the Mercury Mariner equivelent engine and you will need to remove the upper intake plenum to replace the plugs. It is plastic so take extra care when removing and re installing. I did not have to use new gaskets. There is a "coil pack" on each spark plug so no wires to change. I would change the air and fuel filter also.

P0301 - Cylinder 1 Misfire Detected
P0316* - Engine misfire detected on Startup (First 1000 Revolutions) Could be a Bad Coil or bad spark plug or a bad wire on cylinder one. Check the plug and the wire first then move to the coil. 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

You will need to replace no 5 and no 6 coil pack and spark plugs. P0316 is random missfire that computer could not detect the cylinder that was causing it,just knew one was missfiring.
Coil packs are common concern on these vehicles. Can get oil leak into the coil pack wells and may also even get moisture into them.
If yours is a 3.9L it may be involved in owner satisfaction program 07M07 or 07N09 in which they will cover them under the program for up to 10yrs or 100000 miles which ever comes first.