Hi All,

I have 2003 Expedition LT (4.6L - 186k miles) and at the end of Feb my IAC died, so I replaced it with a motorcraft part and everything was good. About month later (March) when I opened my car window as I was accelerating @ a green light I heard a loud rattle. I pulled over and put the car in neutral and park and revved the engine and I didn't hear the rattle. When I pulled out of parking lot I noticed the noise again. After doing some online research I replaced the MAF sensor and ran a few tank fills of high octane gas but nothing seemed to work. What I have observed is that when I first start my car and drive to the main highway there is no noise when accelerating, but once I get to the highway and stop at the first traffic light I here the noise when I accelerate from 0 mph. If I stop somewhere and shut down the car for a few minutes the noise doesn't immediately start after restart and drive it usually takes a few mins to get going. The best way to describe the noise is a loud clanking rattle that only occurs when I am accelerating, it is loudest between 1000-2000 RPMS and I have started to notice that it is even louder on warm days.

To date I am not getting any error codes and my check engine warning light has not gone off at all. My car is accelerating normally so I'm not sure if the issue with engine or if it is some other part. I was able to capture the noise when accelerating and posted the video on youtube (link below). Is was windy day when I filmed but you can hear the rattle in the first few seconds of the video.


Thanks in advance for any guidance you can give.

 

Everything you describe, and the video, I just went through and fixed last week on my Expy. Mine is a 2003 5.4 with 146,000 miles. It was the driver's side second catalytic converter. One of the elements inside had worked loose and would rattle when the case got hot and expanded. I noticed it in April and it steadily got worse as I paid attention to it. Since it was the secondary cat, downstream of all O2 sensors, and my county doesn't do any emissions check, I cut off both secondary cats (to keep it balanced) and replaced with straight pipe. No more rattle, no check engine light, maybe a small difference in exhaust tone, but not obvious. Since I have a welder, it only cost me a day of time and $15 for 2.5" exhaust pipe. If you have emissions check and must replace cat, you can get a single universal replacement for about $120 (not installed), or get a whole replacement piece with both cats by Walker from Amazon or Rockauto for about $270 (not installed).

 

I have an 03 Expedition with the 5.4. I am new to the forum and have been looking for a conversation on the 03 - 5.4.

The engine runs rough when it is cold and actually behaves the same way when it rains a lot...almost like it has a moisture issue at times? I changed the plugs, coil packs and the IAC Vavle..and it still runs rough first thing in the am. I brought it to my mechanic friend and he stated it has everything to do with slow oil flow getting up to the cam and throwing off the variable timing...I am only repeating what he said, I am not knowledgeable enough to go beyond that.

My question is this: The check engine light has been on for 2 years because the code it keeps throwing is for an o2 sensor. Could a cold / plugged catalytic converter cause the truck to run rough when cold?

My mechanic friend is confident in his diagnosis and said just drive it until the engine dies since it is not worth the $$ to do all the cam, timing chain and a screen at the top of the engine that gets plugged, supposedly stopping oil to flow up to the cam.

The engine has 240,000 mile and actually runs great when it warms up. I have been running MC 5w-20 in it as recommended for years. I can turn a wrench, but I am not knowledgeable enough or experienced enough to dig deep into an engine.

I am still trouble shooting and hoping it is not the oil flow issue up to the cam. The engine does not make any knocking noises at all.
Thoughts?

 

Thank you so much!! I knew I was going to need the direct fit because I have no welding experience at all. I found a really good deal to get both driver and passenger direct fit cats (Walker) so I got both of them done. My bolts were so badly rusted I had to take to my mechanic to change them out. I told him to leave the sensors since I was not getting any codes which was a mistake because now I'm getting code P2195 bank1 driver side. Oh well, live and learn. I'm going to try and change myself, it looks like the connector is going to be tough to reach. Did you change your O2 sensors?

But the great news is no more knocking!!! Thanks again and for anyone thinking of doing this or having this done you may want to update the sensors also, especially those front sensors because their connectors look to be the hardest to get to and it would be easier to replace with the unit coming out.

 

Awesome, glad to hear the knock is gone. I didn't replace my O2 sensors. They came out easy and the wires looked good. Before trying to change it yourself, you should ask your mechanic about it since he was working with it.