This is a very long but detailed post so please bare with me.

I bought a 2007 Expedition EL Limited about 1 year ago. It currently has about 135k miles. It came with a third party aftermarket warranty (i dont care for that but they gave it to me for free, $1,500 worth, since they broke a spark plug while replacing them and I had to wait a few weeks to get the vehicle).

After a few weeks of driving it it started to "bog" down and loose its power. It also had a "shudder" around 40-50 MPH and the RPM Gauge jumps around a couple hundred RPMs when it happens.

I was getting a misfire code for cylinder #5 and replaced all the spark plugs again (I know about them breaking off) with Ford MotorCraft and after market coils. I still had the misfire so I replaced the fuel injector on #5. That fixed the misfire code but it still "bogged" down and had no power.

I took it to the shop that dealt with the warranty company and they had it for a couple days. They said the catalytic converters were bad and need replaced but they warranty didnt cover it. They wanted BIG $$$ to replace them so I took it home since Im pretty mechanical and thats a easy fix.

After searching online and found out clogged cats can cause that I gutted the driverside cat and that fixed the "bog" issue. I ended up replacing both with universal cats (the passenger side wasnt melted but figured why not replace it anyways) and that fixed everything BUT I still had the "shudder".

I took it back to the same shop for the "shudder issue". After reading online i was thinking that it was transmission related and it was the torque converter. Even the shop agreed when I drop it off by the symptoms i told them. They called me back and said it was NOT the the torque converter and they think it is the PCM. They said while they had there scanner/computer hooked up it would "loose signal" and that the PCM hasnt been updated. They were going to look farther into it and call me back.

They called me back and asked when was the last time it had spark plugs and coils replaced. I said I did it a few months ago. They said there is misfires on all 8 cylinders but its not enough to throw a code ( I thought if its consistently misfiring on all 8 cylinders it should throw a code...). The truck always had a VERY MINOR rough idle but nothing to really make you worry about it. I also told them I replaced the cats due to a bad fuel injector. They said they think there is a clog some where in the exhaust and wanted to remove everything and hook there computer back on it to see if the misfires go away. Remember the exhaust is NOT covered by the warranty company and I would have to pay for it. I told them I honestly dont think thats the problem because I just replaced the cats and still had the shudder before n after doing it.

I picked up the vehicle they showed me a live feed on the misfires but it was only misfiring on #5 and #6 at the time. there computer was only showing -1 or -3 misfires for those cylinders. I brought it home and ordered 8 new aftermarket ignition coils. I replaced only #5 and #6 coils and started the truck. It ran a lot smoother. I noticed there was a "hard" glob of dielectric grease inside the spring. So I pulled all of the coils and replaced them. I used a que tip and only rubbed dielectric grease in the boots (not inside the spring) and reset the PCM.

Took it for a driver and the engine ran and idle a lot smoother but I still have the "shudder" around 40-50 MPH. If i slowly accelerate it will "shudder". If I accelerate fast it really doesnt "shudder"

What else should I do to help fix the "shudder"?? Other than that the engine runs perfect now. I was thinking about replacing the PCM with a re-manufactured one with the latest update loaded on it. I forgot to metion the shop also said the fuel pressure was good

 

I wasnt sure if I should post this in the engine forum or expedition. Please move if needed.