P0304, Misfire

[xJohnnyOx]

Hey all,

Came back from an out of town ski trip this weekend and my 2000 Expedition EB Model (V8-5.4L) was running rough as I came back into town and it turned on the CEL. Felt like a bad cop (last time I had one go bad was about 5 years ago). Scanner showed code P0304 (lucky me, cyl 4, passenger side, most rear).

Problem appears to also be temperature related. Ran smooth for about 30 seconds the next day (starting at about 32 f temp). Accelerated smoothly until the engine started to warm, then mis-fire started back up (after about 30sec of driving). This happened two days in a row.

Swapped Cyl 4 and 5 cops. Problem stayed with Cyl 4 (Code P0304 came back on pretty quick).

Swapped Cyl 4 and 1 Sparkplugs. Ran good for about 10 minutes of driving, then mis-fire came back, same code P0304. Again, it appears that there is also a temperature component to this issue.

OK Gang, what's the next step???????

Thank you in advance for any help or advise!!!!!

JohnnyO

 

[Trainmaster]

You don't mention how many miles on this old girl.

First try checking that fuel injector and its connecting wire. You may try swapping it with another one.

Otherwise it could possibly be a head gasket problem which is a known machining issue atop the #3, #4 cylinder that sometimes shows itself around 200,000+ miles. Check the joint between the head and block in the vicinity of the starter by the #4 cylinder for oil or water leaking. You may then want to do a test for exhaust gas in the coolant with a special kit or do a pressure test of the cooling system. Hopefully this isn't your problem.

 

[xJohnnyOx]

Eddie,

Thank you for the reply.

249,000 Miles. There was a bit of oil in the spark plug well at Cyl 1, and more in the spark plug well for Cyl 4 (that is, the spark plug socket was oily when I pulled it out). I was thinking that the next best thing to try was the fuel injector. The wiring looks good and I had the #4 injector connector off a couple of times while swapping the plugs and cops.

I will report back after trying the fuel injector swap.

In regards to the machining issue, would it be sensitive to the engine block temperature (i.e. when cold, it runs fine, but after about 30 seconds, it starts to misfire)?


JohnnyO

 

[Yupster Dog]

Problem stayed with Cyl 4 (Code P0304 came back on pretty quick).

Any problem with CYL 4 and 3 The first thing I check is the plastic T in the heater hose to see if it is leaking.

 

[xJohnnyOx]

Yupster Dog,

Good thought. I replaced that T a couple of years ago and it is dry as a bone.

Thank you for the reply.

 

[JVinOlathe]

P301 a lot if the time comes with P301 and 9 out of 10 times is one of 3 things PCV valve, perticularly the rubbet elbow next to it; easy and inexpensive fix. Next is the MAF sensor, you can carefully clean it only with MAF sensor cleaner as any other cleaner or s oil solvent will damage it;. You can also test it with a violtmeter; there are videos on how to do it.
Last is a vacuum leak; some leaks are obvious and easy to find and some, such as those on the throttle body or intake are more difficult to detect. There are several methods to detect vacuum leaks including spraying starting fluid around the vacuum hoses and checking for changes in the iddle speed. Propane works better as it will go places where starting fluid will not but, the best method is a smoke test. Most shops can run it and runs normally under $100 and will find leaks that the other methods will not.
The symptoms you describe are typical of a vacuum leak that often manifests itself with temperature changes as the hoses and joints expand and contract.
One last thing to check is that the throttle body is clean. Sometimes, gunk builds up and also results in similar symptoms.

 

[Dustin Gebhardt]

I had a handful of misfires on my '07 and the pigtail for the COP was bad. The rubber ring around the plug had fallen apart and was preventing the connector from fully seating. I ordered a set of 8 from amazon and replaced all of them, using water-tight, self-soldering butt connectors.

Pigtails:

Amazon.com: 8pcs Modular Ignition Coil Connector Pigtails for 4.6 5.4 6.8 Ford Mustang Cobra : Automotive

Buy 8pcs Modular Ignition Coil Connector Pigtails for 4.6 5.4 6.8 Ford Mustang Cobra: Coils - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

butt connectors:

Amazon.com

 

[jimbosidecar]

I had a similar problem with my 2001 5.4 liter Expedition. Turned out it was a miniscule leak from the thermostate housing. When driving it blew the water into the #4 sparkplug hole somehow. Replaced the housing and no more misfires and no CEL