Bought my 150 - 5.4 brand-spankin' new in 2005. Recently starting running rough so I decided to change the plugs at a little over 156,000 miles. I read all the horror stories about breaking them. To make a long story longer, I ordered the OTC Ford Spark Plug removal tool from Amazon and decided to go with a cold engine. They all came out in 1 piece except #4. So I now also have a Lisle Broken Plug Removal Tool. . . I was shocked how slick the Lisle tool worked.

Anyway, replaced all 8 plugs with Motorcraft plugs. It ran so rough afterwards that I couldn't keep it running long enough to get it backed out of the shop. So I bought a couple of Duralast coils from AutoZone and played "chase the bad coil around" for a few days until I lost track of where the two new coils were.

So I finally ordered a set of 8 Motorcraft COPs. New MC plugs, new MC COPs and still won't run worth a dang. It smooths out just a bit if I can get it to throttle up over 2000 rpm but as soon as I take my foot off the gas, it chugs down and dies. Absolutely no codes thrown. Where to turn next?

I'll keep the OTC and Lisle tools because my wife's '10 Expedition with the 5.4 just hit 100K miles and I 've got to do it all again. I think I'll just replace 1 plug at a time and drive it for week before I replace the next one! It'll take me at least 8 weeks but maybe I'll at least be able to isolate the correct cylinder! Did they fix the breaking plug issue by 2010?

Luckily I still have the '01 F-350 dually w/ 7.3 to get around in. And the 2014 Focus. And the '93 F-150. And the '78 Ranchero. And I can always chug the '48 8n tractor to town if necessary! No bowties on my place.

 

I would say it is not the coils or plugs.. You can have a couple bad coils and the truck would run on the other 6, but NOT GOOD.

Something that would cause bad running is a vacuum hose left off, a harness plug not seated good, or a sensor that got damaged during plug removal... look for other causes... vacuum hoses is a good start.

 

I would connect a scan tool and see if there are any codes to point you in the right direction. Like for example, if you forgot to reconnect the MAF sensor when you reconnected the intake duct.

 

Thanks for the responses so far. I have a scan tool and it threw a few misfire codes when I was chasing around with the duralast COPs. Now that I have replaced all the COPs with new Motorcraft COPs, I cleared the codes and it hasn't thrown any codes at all.

I think I'll go get a vacuum gauge next and see if I can figure out anything from that.

The throttle body has a sensor on each side. I think one may be the TPS or is that on the pedal like on my 7.3? What is the sensor on the other side?

I've been over it several times looking for anything not hooked up.

Thanks again.

 

Did you put all new boots on plugs, boots go bad with heat and age . They have to insulate 5 inches of springs running 30,000 volts from jumping to the head . Did you use dielectric grease on each end of boots . Clean your connectors to the cops , don't use dielectric grease on them it is not conductive .
We no longer use anti seize on plugs ,the new plugs don't break off . Anti seize and dirty fingers causes tracking .Anti sieze on plug tip will short it out . It is a very good procedure to clean each cyl tip area with carb cleaner . If the carbon is so bad that it breaks off some plugs on removal , what do you think it does to new ones being forced thru it .
We have had many reports of new plugs being bad this could be why .
Plus it screws up heat range of plugs .

 

Remove the VCT solenoid electrical plugs and see if it smooths out.
If yes the cams are advanced and you need to find out what parts are causing it. Oil pressure might be involved. VCT solenoids might be varnished up and sticking.
You have to get into good diagnostics and not do so munch at random hoping for an easy out..
Good luck.

 

It sounds like a stupid question, but I've done things like this before: are you certain you plugged back in all the connectors running to the COPs? MAF plugged in tight?