P0304 and P0316 after plugs/wires replacement
 

My daughter's 2004 Mustang V6 started sputtering whenever load was applied at higher RPM's right after an oil change at a local NTB Tires last week. It was running perfect before the oil change. Their technician scanned for codes and told me that it was due to multiple misfires in cylinders 3, 4, and 6. But when I asked him for the codes, he couldn't remember them. They said that the car's catalytic converter was probably failing. I smelled fish right there and then.

I changed all the plugs and wires this morning after work. I did them one at a time to make sure that I don't accidentally place the wrong wire on the wrong plug. The coil pack number arrangements read as follows:

TOP: 1,2,3
BOTTOM: 5,6,4

Once I started the engine after replacing all the parts, it sputtered like a smoker with Emphysema while idling! I realized that coils #4 and #5 were somehow interchanged. As far as I know, not by me. I switched the coils and the idle quickly went to normal. Either way, the car seems to have gained more power after this maintenance.

However, the "service engine soon" light came up so I took the car to Autozone after a brief run on the highway and had them scan the codes. The ECU threw out these codes:

P0316: Crank Sensor Condition
Explanation: The crankshaft position sensor signal is monitored for errors.
Probable Cause:
1. Crank sensor defective
2. Check connector and wiring to sensor
3. Check trigger wheel for damage

P0304: Cylinder misfire detected - cylinder #4
Explanation: The powertrain control module monitors the crankshaft speed and has detected a misfire condition.
Probable Cause:
1. Ignition system fault-spark plugs, ignition wires, coil
2. Vacuum leak
3. Injector fault
4. High or low fuel pressure

IMO, these codes were thrown because of the initial misplacement of ignition wires #4 and #5 on the coil pack. I asked the sales guy at Autozone to reset the codes so that I may eliminate this possibility, but he said that they're not suppose to do that due to liability reasons.

What do you think? There is still a slight sputter every now and then when you push the pedal to the metal, but not as pronounced as before. Like I said, it's gained some power and seems to run a whole lot better.

What kind of plugs are you running? If they are platinums, yank em and toss em in the trash. I recommend NGK TR5's on a stockish 6er.

BTW, #1 is the passenger side front cylinder, #4 driver's front.

Disconnect the battery for about 10 minutes and then let us know what it does.

Oh man! Yes, they were Autolite platinums! I'll disconnect the battery and update you on what happens. I may go ahead and get the crankshaft positioning sensor if it doesn't improve. Thanks for your reply!

Don't get the crank sensor without first resetting the codes and if any pop up, tell us what you have.

I double checked the numbers on the coil pack yesterday morning. They read as follows:

TOP: 1,2,3
BOTTOM: 5,6,4

I tried switching the bottom wires in every configuration possible (e.g., 4-5-6, 4-6-5, 5-6-4), but the only combination that works is the 5-6-4 as indicated by the numbers written on the coil pack. Otherwise, the car idled terribly like a coughing rooster.

I placed the wires back on the coil (5,6,4) and took it for another spin where it sputtered again going uphill. It almost felt worst that before. I took it home and disconnected the battery for about 15 minutes before reconnecting. I then went to bed (I work the night shift).

I spoke to my daughter before coming in to work and she said that the car didn't sputter at all when she drove it to work. I scratched my head and told her that it probably won't last. Sure enough. She just called me to tell me that the car did it again on her way home from work - uphill. The "service engine soon" light also came back on.

I'll take it back to Autozone to be scanned and see what engine codes are now showing. TO BE CONTINUED...

I went to Autozone right after work this morning and had them scan for codes. P0304 was the only code. According to their printout, probable causes can be any of the following:

P0304: Cylinder misfire detected - cylinder #4
Explanation: The powertrain control module monitors the crankshaft speed and has detected a misfire condition.
Probable Cause:
1. Ignition system fault-spark plugs, ignition wires, coil
2. Vacuum leak
3. Injector fault
4. High or low fuel pressure

I've changed the spark plugs and wires. I replaced the MAF filter (K&N) and added one bottle of Lucas' "Tune-up in a Bottle" fuel injector cleaner. I seriously doubted that it was a vacuum leak because I've experienced one with my Audi before and the symptoms were much different. Only thing left to do would have been to replace the coil pack and/or fuel filter.

I opted for the coil pack replacement and, freaking hopefully, I believe that it fixed the sputtering! I took the car for a quick ride up the long massive hill which have been my test track for the past few days and not once did I feel any hesitation. I better not get too happy about this. I may jinx my own success.

If indeed the coil pack turns out to be the culprit and the car continues to run smoothly without any sputtering in the coming days, it has been a pleasure exchanging ideas with you guys. Special thanks to RyansQuick6 for his effort and willingness to help!

On the other hand, I may be back again with a completely different problem. I only hope that it won't be too soon.

I hope you got a motorcraft coil, our at least one with a lifetime warranty. Don't be suprised if the issue shows back up, but swap out the coil first if its not a motorcraft

I've had the same exact problem. On my 2002 its 123 up top and 465 on bottom. My car was doing the exact thing. I replaced EVERYTHING I could think of. Eventually it all came back to the ignition coil again. Sounds like if you replaced that coil you should be good to go

@ RyansQuick6: The old coil which went bad was a Motorcraft. I could only get my hands on a Duralast with a 2 year warranty for $70.00. I'll try to get a Motorcraft or one with a lifetime warranty next time. Hopefully, not too soon. ;-)

@ Cj02stangV6: I hope so, too. Thanks!