Hello everyone! I am wondering if someone can please help me narrow the possibilities. I have a 99 4X4 expedition with a 5.4L. It suddenly began sputtering (in all fairness, I accidentally pumped 2.5 gallons of 89, which my SUV does not like), but I have already refilled and the sputtering continues. I checked the coil pack for the #3 cylinder per the code reading "Misfire in cylinder 3"and it tested as good--using an OhM meter. I also replaced the plug in that cylneder just to be on the safe side and the plug that was in there--seemed good. The sputtering did stop for a moment, but came back. The exhaust smell is like "fireworks". I checked for vacuum leaks and I can't find any (using the gauge). The gas cap is OK. One other note worthy comment--in the AM or after sitting for at least 5 hours, it needs to crank (for more than normal) seconds before it starts up. That's about it--any ideas anyone? BTW, it has 171K and has been kicking hard and strong prior to this. I have always dilligently kept up the maintance AND I did change the PCV valve as a precaution----one last thing--the "Service Engine" light is flashing and then stays on and after a while goes back to flashing, but the only code that comes back is "misfire in cylinder 3" Any ideas? HELP. Thank you all.

 

what color was the spark plug that came out?

Sounds like you have several posibilities:

also, since you are saying you are getting a sulphur (fireworks) smell, I'm certain you are dumping raw gas down the exhaust via cylinder #3. That smell is the Catalytic Converters trying to due their job, but are being overwhelmed.


quick easy test you can do though on the COP. Swap it out with the COP from another side of the engine. If it is the problem, you'll see it appear on another cylinder almost immediately


Hope I am some help for you

 

The materials in the rubber boot for the coil pack tend to break down and allow spark to jump to the side of the spark plug well. So even if both the COP and plug are good, you can still get a misfire. Some auto parts stores sell a set of 8 boots for around $25.

 

Thanks guys. I tested the EGR Vacuum Regulator and it checked out in terms of the OHMs. I also tested the DPFE (Differential Pressure Feedback Sensor) sensor. I did two tests, the first was to check the voltage using the Ground and Ref and it checked out between 6 & 4 volts with the Key on the ON position. However, when I ran the test for the signal voltage it ran at .22 cold (which is normal), but only climbed to 1.35 with the engine at normal operating temperature and the manual says that it should have climbed to 4.0 - 6.0. Two questions--My truck has 170K+ miles and this has never been changed. Can it be bad? Can this be causing the misfire / sputtering to happen? I like the idea of swapping the COP with another plug and see what happens.

BTW, the plug that I removed was normal looking---a pinch whiteish, but no ash. I compared it to the book and it looked most like the "normal" wear picture. Thoughts?

 

a good plug should look like dry fresh coffee grounds...light brown color. No white ash



before you start throwing parts at the truck, swap out the COP and see what happens

 

Running the lower octane gas may be your problem.


Our new Ford COP’s, the Sultans of Spark(S.O.S.), have
been designed with both durability and performance in mind.
Please see them at:
Ford SOS Coils
Quality was the main feature we stressed when we went to the
drawing board on these coils.
By the way, for those of you who only need to replace a defective coil,
our SOS Coils are available separately.

 

Well guys--it ended up being the coil pack. I changed it and problem solved. Thank you all for your help and feedback!