The truck with the O2 sensor showed misfires on various cyls only in mode 6, I don't think it ever set a P0 misfire code on the same one.

 

The truck never sounded like it had a miss but it runs rough immediately after startup on mornings below 20F. The new battery is nice. I swapped #1 fuel injector with the #3 injector. I cleared the code when I removed the battery and nothing else popped up during the test drive. I'll test it again in the morning to see if I can get it to throw another code. I'll keep everyone updated. Thanks for the help so far, everyone!

 

If that doesn't work, I'd swap out the cop and boot with another cylinder and try it. I had a boatload of problems with the cops on my my 00 super duty and that was the only way I could figure them out.

 

Quick update. I added some fuel stabilizer to help with the soot. I swapped out the #1 and #3 injector. I did all of this on Saturday and I've had no problems since. However, the temp hasn't been below 32F since then. I don't normally get a code until in the mid 20s or below. We'll see what happens, only supposed to get warmer this week. 50's by Friday.

 

Sounds like a 1987 truck that I had (first model with CPU) but it would lose the signal from the distributor (RPM sig). It would promptly go into limp mode. Would only do it when it was cold, btw. I replaced everything that had something to do with it to no avail. I got a battery operated O-scope and it confirmed that the wire was either shorting or bad. I removed the junction box on the firewall, planning to rerun the wire. I freaked when I saw all of the silicone grease and promptly put it back. It never happened again. Reseat fixed it.

 

I am really frustrated. I just bought a 2005 Ford Expedition Eddie Bauer 5.4L Triton with 160,000. Drove it home from the dealership and the next day the check engine light comes on. Code P0303 pops up and we take it back to the dealership. They told us before we bought it that they changed all the spark plugs.
They tested it at the dealership and code P0303 pops up so they replaced the #3 coil. Drove it home and later that night the check engine light comes on again. Took it back to the dealership and they said that is still showing P0303. They are keeping over the weekend so I hope they can fix it for good so I don't have to keep taking it back.
There is NO warranty due to the high miles but they are being nice and checking it out since we just bought it from them. I called and suggested that they check for a leaky valve or vacuum pump like I read on this forum and the service manager sounded annoyed.
Any similar situations with results would be greatly appreciated.

 

Update.......We picked our Expedition back up after they said the fuel injector needed to be replaced. Was driving good for the week and the check engine light just came back on. Had Auto Zone check for the code and guess what.......P0303 again.

 

Has the COP harness been checked for an open or short or bare wires that could ground out causing a misfire? Has the COP boot been replaced? Could the plug be defective? Is the COP defective? Has the injector wiring been thoroughly checked? Is the injector flowing properly? These are all things that could cause a misfire.

 

I will be dropping my Expedition back off at the dealership and will be showing him the list of things that you said Greg B.
I hope they can get the problem fixed.
Thanks for your suggestions Greg.

 

I hope they can fix it as well. Let us know how it works out for you. But if it comes down to you having to pay for the repair, you might be better off taking it to an independent shop. It'll be less expensive and you'll probably get better service. If you don't know where to take it, ask people you know who they use for auto repairs and about their experience.

 

Well guys, it's been a month and I'm still getting misfire codes for Cyl #3. I've also got a Random Cyl misfire one time and I've started to see this code for "Post Catalyst Fuel Trim Too Lean Bank #2". This is the side opposite of Cyl #3. I've done research and found that a misfire can cause that code to pop up. It seems to be random days and random times when it misfires. Normally the truck is setting in my driveway warming up when the light comes on. Let's recap everything I've done since October:


8 brand new plugs
New coil boot on cyl 3
Replaced head gasket (took to a mechanic, did diagnostic, didn't fix)
Fuel system cleaner
Fuel injector cleaner
Fuel stabilizer
Cataclean 02 sensor cleaner
Changed from Unleaded to Premium
Changed air filter
Swapped fuel injector #1, #3
Replaced coil wire for cyl 3 (just this past Saturday)
Replaced battery
Replaced Alternator




I'm well over $4,000 into parts and false solutions chasing a misfire that only misfires for about 30 seconds when it is cold. I'm also only getting maybe 12.3-12.8 average mpg mixed driving. I'm half tempted to trade it in for a newer model. It never gave me problems until it got cold this winter. What is going on? What could cause this?

 

You aren't alone KP. I for one have spent a small fortune for some code that won't clear. It sure sounds like to me that there's a wire involved. I'd trace it from Cyl 3 on back to the origin. I mentioned before that I had a similar issue (at the beginning of the ECM era, ECM was losing the RPM signal) and it was only in the winter. Sounds like the truck isn't in closed loop when it happens. I'd feel the wires to make sure that they still have the insulation. You may also want to get a obdii 2 interface (I recommend the PLX KIWI wifi if you have an iphone). That bad gas mileage may provide a clue. I'd check the long term fuel bank 1 and 2 (they should be close to zero and +/- 10).

 

What brand of coil packs are you buying. I chased mis fires until I put all new Ford Motorcraft coil packs on my 06. I wasted $200 on Axcel yellow coils that lasted 18,000 miles. I hear the Grantelli 's with lifetime warranty aren't any better than Axcel. The mechanic at my dealer said most times its aftermarket coil packs.

 

Has anyone checked compression on this engine? What if it has lower than normal compression when cold. I have seen this before. A leak down test could help diagnose a worn cyl or valve..

 

The wire was chased back to the origin and replaced for Cyl 3.

I used a Motorcraft coil pack for Cyl 3. When I got it back from the mechanic he accidentally switched the coil pack for 2 and 3 and the misfire was still on 3.

I think I'm going to take it to Ford this weekend and have them just run a diagnostic on it. I try to do most of the work myself if I can but I just can't figure this out. If I keep trying I'll probably spend enough I could have bought a second vehicle.

This problem just bugs me because it's only when it is COLD outside, during a COLD startup and 99% of the time the truck is idling in the driveway when the light comes on.

On 2 occasions the light came on while I was driving. The first time was when I left work and gunned the motor to 75 mph on I-44. The second time was 2 weeks ago when I left for work and gunned the motor to 75 mph on I-44.

I just don't understand what could be wrong with it.