Hello all, been a long time since I have posted on this forum.

I need some help/advice.

My 07 lariat with the 5.4 has 201,000 miles on it. I've put about 100k of those on myself.

Truck has always ran pretty good. One day I got a P0018 code and replaced the cam position sensor. The CEL went off and I am showing no codes.

While I was in there I replaced all the plugs and coils.

Now I have a rough running condition that won't throw a CEL.

It only occurs in OD from 40ish to 50ish miles an hour. Once I get up to 60 the truck runs fine. When it isn't in OD the truck runs fine. The truck vibrates and it files like I may be running over a rumble strip.

I don't believe it is a trans problem, it seems to lie with the motor and engine load.

I am leaning towards replacing the front two O2 sensors as I have seen something similar to this on another vehicle.

Any pointers would be great.

 

what plugs and coils did you use? Motorcraft? that to me sounds like you have a coil that is starting to go bad

 

Plugs are motorcraft - latest rev that just came out last year.

The COP's are DENSO. Not the cheap ones on Ebay, I got them from rock auto.

Surely brand new COP's aren't failing?

 

I did save the old COP's, guess I could put them back on for a test.... I think all but one were motorcraft.

 

Sounds like a misfire; hammer on it when it does that to get it to throw a code. As the running condition occurred after the plugs/coils, logic says they're related. I'm learning just how senstive these engines are to plugs/coils, so I'd retrace your steps. Proper torque on plugs, clean boots, slight amount of dielectric on the boot where it contacts the porcelain, try and keep the metal part of the plug and boot spring clean of grease. Ensure they're installed all the way, and your electrical connections tight.

When I replaced my coils, I had 1 that failed within 400 miles, so it's not out of the realm of possibility that you have one that is bad right out of the box.

What brand plugs and coils did you use?

 

See other post... Die electric grease was used as well.

 

I will say I believe I had a low grade miss before I changed the camshaft position sensor.

The trans would jerk occasionally going up a hill in OD. Basically when the engine was loaded.

 

just because they are new doesn't mean they are good. I've seen motorcraft ones bad right out of the box

 

You have a point. I work in Tier one automotive manufacturing. I see it everyday!

Guess my next step would be to order 8 new motorcraft one.

Trouble with the Denso ones is I sat on them for 9 months before I got them installed. I was very busy building a new house.... Basically no chance of returning them.

 

Maybe too much grease... its non conductive. Did you drop a plug prior to install ? over tourque of a plug can crack the porclin ... this will cause a mis-fire condition like you are explaining. Double check all your connections to COP's and injectors. Like stated above .. hammer it when its misfiring .. look at CEL flashing... pull DTC's then we can see which cyclinder it is.