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Discussion Starter #1
Hi,
My 2003 Taurus (Duratec) with 82k mikes is misfiring. It's most apparent when parked in gear. It misfires enough so you can feel it in your seat. When I put it in neutral the misfire mostly goes away but still happens to a small degree. Then while still in neutral it will misfire just like in park if the A/C is on. So, it's most evident when a load is put on the engine. But it's not that apparent when driving. I'm not even sure it is. I should note that I recently changed the spark plugs about 1k miles before the misfiring started. So far the engine light has only come on once.

Any investigating I've done on the group tells me it can be anything from spark plug wires to coil to cam sensor to vacuum leaks to pcv/egr valves.

Then I found out Autozone will do a free scan. Their scanner reported P0300 and P0316. The print out for P0300 showed general misfire and general causes like spark plugs, wires, coil, vacuum leak. P0316 showes the crank position sensor as a possibility. This was interesting since other folks have stated P0316 is the result of misfire in the first 1000 rpm's but I have the printout stating CPS.

Since the CPS looks like a pain to change I thought I would check in and see what others think. Any suggestions? I'm hoping I won't be replacing part after part to fix this thing.

Thanks!
 

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I would replace your spark plug wires at the very least, especially since you had just replaced the plugs, just because its part of a tune up, and your mileage is high enough to where replacement isn't out of the ordinary.

The P0300 is a general misfire code, and as you have already stated can be a result of numerous things. Coils, wires, plugs, injectors, sensors, mechanical issues etc. Being that you are throwing a P0316 in conjunction with the P0300, I would think that they are related, but rather than throw money at the vehicle, do a few things first.

Replace your plug wires, chances are they are at, or close to the end of their life as it is. Check the connector going to the CPS for corrosion or a poor connection, clear the codes at advance auto, or autozone and see if the P0300 and P0316 codes come back. In the event that the codes do come back, or just one of them, you can rule out the possibility of the plugs and wires and move on to more possibilities. If the scan tool at whatever parts store you go to has the ability to monitor misfires, this could be a helpful tool to identify which cylinder(s) the misfire(s) is/are isolated to. I don't know if the scan tools they use have this function, as I have never inquired about it. In the event the spark plug wires don't fix your issue, and it is isolated to a specific cylinder, or group of cylinders it could tell you where to look next.

Good luck, and I hope you resolve your issue!
 

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Well, you're the second person in about an hour's time with the exact same codes with the same engine on a car that's one year newer. Coincidence?

In your case I would start by checking spark on all cylinder. You might have a weak coil.

A slight misfire and rough idling can also be caused by vacuum leaks, so start checking all the hoses. Like I told the other guy, the Duratec is somewhat of a vacuum leak monster. Pay particular attention to the PCV elbow under the throttle body. They're also known for leaking intake manifold gaskets (especially if you notice a bad cold idle but the idle is better when the engine is warmed-up).

P0316 is Misfire Occurred in the First 1000 Engine Revolutions. Ignore those Autozone explanations because they just want to sell you parts.

Codes might be electrical/PCM related, so check your battery. Some have experienced a resolution after getting the PCM re-flashed at a dealer.
 

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Discussion Starter #4 (Edited)
Thanks guys. I'm realizing I will need to take a systematic approach here. It does make sense to change the wires considering the age and mileage of the car. I plan on buying Motocraft wires and will probably get them at parts.com that I have used in the past.

I should mention that the misfire at idle occurs a little randomly. I feel the bump like every one or two seconds. It's not a continual or constant rough idle. For that reason I didn't suspect the coil but who knows.

I will check the CPS connection. It didn't make much sense the sensor would be bad as I would have expected much worse symptoms. But, the fellow at Autozone was very enthusiastic as this being the problem as he had seen it before. I got a little suspicious when he said the crank shaft sensor and cam shaft sensor are the same thing.

Behlinla, I liked the video but my coil is buried under the intake manifold. Doesn't seem like a practical test for my particular Duratec. I used to do this test on my Datsun 510's back in the day but the first time I tried it on a modern car I got my ass kicked across the garage! Must of been bad technique. I also heard this is a good way to damage a coil but it must be OK if done quickly and a wire not left off for a long time.

Thanks again,
Steve
 

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Yes, I forget the coil pack was way back there, so I agree that test would be more difficult to do. And yes, you don't want to be jumping the spark way out or not grounding the coil for more than a few seconds so it doesn't overheat.

What you could do instead is just take the coil out of the car and do some resistance checks on the primary and secondary coils, along with a detailed visual inspection for small cracks.

Yes, you car does have separate crankshaft and camshaft sensors (they're both in the front cover). The guys at Autozone think they know everything.
 

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The cam position sensor (really called the CMP) on the Tec NEVER fails. Its the Vulcans that are known for CMP / syncro failure.

I am betting on a bad coil pack.
 

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Does this engine have a "wasted spark" ignition system? Since the misfiring started shortly after replacing the plugs, I can't help but wondering if you replaced the plugs with Motorcraft plugs. Ford "wasted spark" ignition systems have problems with other brands of plugs. If it is the plugs, the spark plug wire boots are now destroyed as well. Do a Google search on Ford wasted spark ignition system spark plugs. Just one of many possibilities you might want to check out.
 

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Does this engine have a "wasted spark" ignition system? Since the misfiring started shortly after replacing the plugs, I can't help but wondering if you replaced the plugs with Motorcraft plugs. Ford "wasted spark" ignition systems have problems with other brands of plugs. If it is the plugs, the spark plug wire boots are now destroyed as well. Do a Google search on Ford wasted spark ignition system spark plugs. Just one of many possibilities you might want to check out.
I have Autolite double platinums in my 01 Tec and it runs great. I also have Bosch platinums in my 98 Windstar and that runs flawlessly too. As far as I remember a "Motorcraft" plug is actually made by Autolite(or the company that manufactures them).

My bet would be a weak/cracked coil pack, or bad plugs due to a lack of maintenance.
 

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Discussion Starter #9 (Edited)
I hope to work on this problem Tues evening. In the mean time I sprayed half a cup of water behind and on both sides of the minifold to see if I could get a light show from the coil. There were zero sparks and all that mist had no effect one way or the other on the misfires.

Oh and I have a bad habit of using Motocraft and Autolite interchangeably. I installed Autolite but I also understand them to be made by the same company.
 

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Discussion Starter #10 (Edited)
Well, I finally got the UIM off to check the coil. Coil looks great with no cracks whatsover. Reistance showed 1.3 ohms on the primary and ~10k ohms on the secondary.

From what I have read on the forum it could still be the coil but I'm tempted to replace the wires before the coil.

Since it had only been about 3k miles since I changed the spark plugs I decided to pull them and inspect. Turns out I used Motocraft AGSF 32FM plugs. They are gaped .055". I was a little surprised about their condition. The center electrodes have a dark shellacked look to them. Like a sheen of oil but could not be wiped off. I just don't remember the old plugs having this look. I'm tempted to replace them before I replace the wires becasue this misfiring happened so soon after replacing the plugs. I suppose the look of the plugs could be due to the misfiring I'm experiencing.
 

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Discussion Starter #11
OK the eyes are getting old. This morning I took the coil pack outside in the bright sunlight an spotted a very fine vertical crack along the back corner. Looks like I'll be buying a coil pack. I'm not in a huge rush so I might mail order one. Any suggestions for a good source?

Thanks,

Steve
 

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Either Motorcraft or BWD. Stay away from the cheap AZ Duralast junk. If you dont mind waiting a few days, get a Motorcraft from Rockauto.
 

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Discussion Starter #13
Jeff I took your advice and got the BWD coil pack to get my wife back on the road with her beloved car.

So the good news is the obvious misfire is mostly gone. Before the coil replacement I was getting an obnoxious misfire about every one or two seconds that was pretty rough. Now it has a slight stumble around every 10 to 15 seconds.

Maybe I'll go back to Autozone to see if it's still throwing p0300 and p0316. I still might change the wires. It's much more tolerable now but not perfect.

Thanks,
Steve
 

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Discussion Starter #14
Took the Taurus back to Autozone after changing the coil pack and good news, codes p0300 and p3016 went away and no codes are being displayed. I still want to correct the occasional stumble I'm experiencing.

The Autozone fellow said I should replace the wires as a bad coils can stress the wires. Not sure I believe him on that point but after 80k miles it still may be a good idea.

I bought a gas filter and injection cleaner for good measure. If I don't see any results I'll go ahead and replace the wires.

Any thoughts?
 

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Discussion Starter #16
I changed out all 6 with Motocraft about 3k before I discovered the coil was bad. Are you saying to change the affected plug again? I took them out for inspection before the coil was replaced as well and didn't keep them in order.
 

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Discussion Starter #17
I don't get it! I just moved the Taurus into the garage for the night. I started it up and put it in drive with the a/c on. With the brake on It started to stumble just as bad as it ever did. It's now leading me to believe replacing the coil pack had no effect even though there were fine cracks on the surface.

Just 4 hours before this episode I had Autozone scan it and it gave zero errors.

Is it time to pay the big bucks and have a shop look at it?
 

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Stumble with foot on brake = leaking brake booster (vacuum leak)

Pump the brake pedal repeatedly at idle. If the engine wants to die, then you found it.
 

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Discussion Starter #19
Theory sounds good but it can care less how often I pump the brake pedal, pumping the brake has no effect on the engine stumble I'm experiencing. The fact that the car is in gear and either parking brake or foot brakes is on creates the increased load at idle that leads to the stumble/misfire. Having the a/c on only adds to the load at idle which encourages the problem.

I have since replaced the pcv valve and rubber elbow when I noticed it had collapsed with the engine running. I also replaced the smaller diameter hose that runs down vertically adjacent to the pcv hose at the UIM when I noticed cracks. While these items needed replacing it did not fix the problem. Perhaps there is still a vacuum leak somewhere I just have not been able to locate.
 

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Discussion Starter #20
Looks like problem is fixed after replacing spark plug wires! I should have done this earlier but I let personal bias get in the way. In my 30 plus years of backyard mechanic experience I have never had the wires cause misfire or stumbling. Just lucky I guess.

So just to sum up, replacing the plugs and cracked coil pack did help with performance and I believe it was the coil pack that did throw p0300 and p0316 and did cause some stumbling but the wires were causing the remaining stumbling I was experiencing. I don't think I ever had a vacuum leak but I did replace the PCV hose because of collapsing.

Got to say the Duratec is a peppy engine and I'm pretty pleased with it over the nine years driving it.
 
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