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Discussion Starter #1
I have a 2002 Taurus SES- Duratec engine - had it two years - CEL has been on the whole time. I have a pocket scanner - it keeps showing P0301 and P0316 - I have cleared the codes numerous times and they keep coming back - I have replaced all four O2 sensors, cleaned the Mass airflow sensor, replaced spark plug wires and spark plugs, checked/replaced bad or loose vacuum lines. Recently, in heavy rain or after spray wash, the CEL started flashing - then it would only flash when climbing a hill - would go back to unblinking CEL after reaching top of hill and leveling out. I took the upper intake manifold off to replace the rear plugs - can remove/replace easily now - could it be the coil pack? or maybe the injectors?

joshaughne
 

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A few pieces of the puzzle to start...

  • The flashing check engine light (CEL) indicates the engine computer has detected the engine is misfiring - and lots of it. You should be feeling the engine struggling to run and 'stuttering'.
  • Electrical basics:
    • The coil generates a high-power electric charge
    • The sparkplug wires carries that charge to the sparkplug
      Sidebar: The computer (PCM) times the electrical charge to get to the sparkplug at just the perfect time when the air/fuel in the cylinder is ready to fire
    • The electrical charge enters the sparkplug and ignites the air/fuel into a controlled explosion (of energy).
  • Electricity will take the path-of-least-resistance, especially if there is water/moisture to travel along
To tie it all together...

If there is any weakness or flaw in the connections between the sparkplug wires and the coil, or, at the other end at the sparkplug, the electrical charge is going to escape, or take a detour and not make it all the way sparkplug!

So in this case, focus your efforts on finding where the electric charge / 'spark' is escaping:

  • review sparkplug wires - make sure they are in the correct firing order and connected firmly

    Might as well do the sparkplugs while you're in there if you did not use double plats
  • Inspect the coil for any signs of cracks or breaks / flaws in the surface.

    Electricity often leaves a light gray-colored track on the surface of the coil - a good indicator of leaking at the wire/coil connection point.
 

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Flashing CEL = bad missfire = damaged cats = BIG $$$ to fix. Do not drive the car until the missfire is fixed. If the engine has been missfiring (301 code) for 2 years, your bank 1 cat is likely already somewhat damaged. The CEL is there to tell you there is a problem that needs attention. Ignoring it likely means more $$$ to repair than if it was taken care of shortly after it came on.

Likely coil pack failure. Use a good quality coil (i.e., NOT AZ junk).
 

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Discussion Starter #4
Thanks for the info. I have taken this car to a local general repair garage and I've spent $1200 trying to correct the problem. The last time, they told me I could fix it myself because they had already run my bill up to $540 replacing coil springs and strut mounts, to pass the Pa safety inspection. I have had a lot of older cars but never a computer problem like this. I'm going to take your advice and replace the coil pack - and I'm going to switch #1 and #4 injectors to see if I get a P0304 code instead of a P0301. If so, it would indicate a bad or plugged injector, right? Here's a question - how does the computer know which cylinder is misfiring? Is there a sensor on each cylinder? If the coil pack uses the "waste spark" system, and each of the 3 coils fires 2 cylinders on every revolution, why don't I have 2 misfiring cylinders?
 

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Thanks for the info. I have taken this car to a local general repair garage and I've spent $1200 trying to correct the problem. The last time, they told me I could fix it myself because they had already run my bill up to $540 replacing coil springs and strut mounts, to pass the Pa safety inspection. I have had a lot of older cars but never a computer problem like this. I'm going to take your advice and replace the coil pack - and I'm going to switch #1 and #4 injectors to see if I get a P0304 code instead of a P0301. If so, it would indicate a bad or plugged injector, right? Here's a question - how does the computer know which cylinder is misfiring? Is there a sensor on each cylinder? If the coil pack uses the "waste spark" system, and each of the 3 coils fires 2 cylinders on every revolution, why don't I have 2 misfiring cylinders?
1) Camshaft position sensor detects when it changes rotational speed without input from user, and looks for repeating patterns, From there the computer says "Hey this is messed up, I believe it is a misfire on #1 due to the patterns"

2) No there isn't

3) Good question but each "sister" isn't connected to each other in such a way that if one doesn't work, the other won't. Fail safe
 

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Discussion Starter #6
MARK OREMAN - Thanks for your answers - I had an old 2 cylinder British bike - a BSA - wouldn't run right - took out the 2 coils and put in a single Harley-type coil - fired both cylinders every rev - so if one cylinder fired OK and the other one didn't, you knew it couldn't be the coil.
 

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Discussion Starter #7
JEFF K - Thanks for your help - I've had and fixed 25 or so cars - Chevys (10), Buicks(2), Olds(4), Toyotas(5), Saabs(3) - and one Mazda - but it was the newest one - a 1995 - computers and codes are Greek to me.
 

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PCM determines missfire using the CKP (crank sensor) to measure the slight acceleration rates of the crank when a cyl fires. If PCM sees a lower or no acceleration (compared to other cyls) due to a missfire it will set a code for that cyl. Its actually more complex than this, but thats the basic idea.

If CMP (cam sensor) was out of sync, the PCM would set a P0340 code.

Has anyone checked base engine parameters, like compression and leakdown?
 

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Discussion Starter #9
Still codesgetting P0301 and P0316

I had a flashing CEL - I replaced the coil pack - now it runs a lot better and doesn't shake and shutter after turning on the AC. But, I'm still getting P0301 and P0316 codes - have cleared it, had it come back 4 or 5 times. Does this mean #1 fuel injector is clogged or defective?
 

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Might check injector, then do a compression/leak-down test. Did you use a quality coil like Motorcraft or Borg-Warner?
 

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Also look for UIM to LIM gasket leak or LIM to head gasket leak (vac leaks).
 

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Discussion Starter #12
I got a BWD Coil pack - (Borg Warner?) - inside the old Motorcraft coil pack, the rubbery filler had baked hard and was cracked - I took off the cowl on the passenger side to get access - much easier than removing the upper intake manifold.
 

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Discussion Starter #14
I used a "BWD" coil pack. Is that made by Borg-Warner? Replacing the coil pack has made the car run much smoother, but the P0301 code still comes up. It seems to be missing when it's cold and then after 1-2 minutes it smooths out, The garage I took it to said they think it's a bad injector on cylinder #1. I'm checking it next.
 

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Discussion Starter #16
Jeff K - I got a gasket set for the upper and lower manifolds - will check for leaks when I go into the injectors. I had the UIM off before and the gaskets were oily and kept slipping out of the grooves - should have replaced them at the time. Thanks again for your help.
 
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