My wife's 2004 5.4 Expedition is having a strange problem and I'm hoping somebody here can shine some light on it for me. The truck has about 120k miles on it and it is misfiring pretty badly both at idle and on accelleration, but it will not throw a code. I put it on a Snap-On scan tool and it read 150 misfires during the test drive but wouldn't show which cylinder is misfiring. Using my old school logic I started unplugging coils while the engine was running to see if I could find one that didn't make a difference but they all did, with the exception of the rear passenger side coil, which I couldn't get to because it was too hot.

Also, there has been a strange vibration/ rattle from the exhause since we bought it (@90,000 miles), but that sound got worse after a long road trip towing a boat and now it happens all the time. I thought maybe it was a broken baffle in the muffler, but I got under the truck and it sounds like it's coming from the driver side cat or egr valve. Anybody on here had issues with broken catalytic converters? If I take it off and the cat is broken is there any way to tune out the rear o2 sensors so I won't have a check engine light all the time after I gut it and put the shell back on? I know it's not the right thing to do, but money is very tight right now and I need to get this thing back to running right.

Thanks in advance guys!

Justin

 

Does your scan tool have Mode 6 capability? Go to the link below and read about Diagnosing Ford Misfires using the Mode 6 capability of Scan Tools (not code readers). I just diagnosed a non-code setting misfire on my 2001 5.4L Excursion using Mode 6 on my AUTOENGINUITY Scan Tool two days ago. It works great.

http://www.motor.com/article.asp?article_ID=1794

 

If the misfire has been going on long enough, it could be that it has been dumping raw fuel through the cats which will melt them.

As far as pinpointing your misfire.... When was the last plug change? Even with money being tight, this is something you need to just save for. The motorcraft plugs are only about 12-15 bucks If I remember. You can pick up a new set of visteon coils on ebay for around 120 bucks. It's just needs done as maintenance. No real way to short cut around it. Been there, broke with mechanical issues and you want the cheap easy fix. For a misfire, chasing it will cost you more headache in the long run so it's best if you can't pin point it and no maintenance has been done the it is best to just change the plugs and cop's.

At this point I wouldnt recommend it but... if you can hold the rpms and conditions that cause it to misfire, it will more than likely eventually throw the CEL and indicate which cylinder it is. Worked for me. But I did it the very day I noticed a misfire.

 

I believe the 04 Expy 5.4 was still the 2V, so the plugs are only about 3 bucks apiece. In fact, SP479's are $2.57 each at rockauto.com.

The Visteon DG508's are about $25 each or $190 a set on Ebay.