Question about 2002 Mercury Sable
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:
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!
Posted on Feb 04, 2012
Just check vacuum lines first. Ford is bad for these. After that I would look at the coil pack. Other things could be at fault. But I always go for the vacuum lines first with both banks throwing lean codes.
Posted on Nov 06, 2015
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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.
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