Today I replaced the plugs in my 03 150 5.4 with motorcraft platinum and cleaned the MAF with contact cleanerand let dry for several hours and now my truck is running Horrible. Its shaking at idle and at 1500 to 1900 rpm's it feels as if it was only running on 6 cylinders. Untill now i have had no problems with the truck except for some hesitation when accelerating.Is there any possibility that a cross threaded plug could be to blame or could it be something else , any response is greatly appreciated.

 

did you gap the plugs correctly? They say they come pre-gapped, but that isn't always the case. A plug that slips down into the cylinder well and hits the bottom can close the gap to under spec, or even totally closed, and that will cause misfiring like symptoms. Also, cleaning the MAF should be reserved in most cases to if you have a problem. You could have damaged it and that would definately cause such an issue (an issue thats over $250 from ford)

 

First of all check carefully that you reattached al the coil plugs properly and that they all snapped into position also check that you did not accedentaly knock off one of the fuel injecter plugs. I doubt that the mass air will cause this problem. if you find nothing in the visual exam, while running remove the injecter plugs one at a time to dissable the cylenders note the one or ones that make NO differance and pull that coil and plug and inspect for dammage. Hope this helps sounds like a closed gap, a bad plug or a coil problem make shure the boots on the coils are ok and that they went in properly visualy check the plug for a crack,Did you put dieletric grease in the boots of the coils??

 

That sounds like a coil to me. When I replaced my plugs last Jan my pickup (99 5.4L) was doing about the same thing as yours. It made the SES light come on. It threw a Ignition Coil D code. I didn't get the little retaining bolt down tight on the coil on cyl. #4. I tightened it down and the problem went away and the light went off. I would also check to make sure you didn't accidently knock one of the vaccum hoses loose.

It also was doing the same thing starting this week. This time it threw out the code P0306 I believe. It was a missfire in cyl #6. I bought a new coil from NAPA for $46. Problem solved.

Has the service engine soon light come on? If it does you can get the codes read at Autozone for free. Post the code on here and someone can give you more advice.

 

I set the gap on every plug at .052" I checked the gap twice , but on the back plugs near the firewall there is a chance that the gap could have been knocked off or I could have cross threaded a plug because it is so tight that it's hard to tell what's happening at the end of that wrench.The SEL has not come on yet I have not driven a mile yet because of the problem. I checked every hose and wire I removed to make room to work. I guess i'll pull the plugs and recheck the gap and make sure the coils are tight on the plugs. It would help to have room to work under the hoods of these trucks. Thanks guys!!

 

Chucks , no I did'nt use any dialectric grease , could that cause the motor to run that rough?

 

If you let it idle long enough, it will probably throw a code if its going to. The computers are pretty sensitive in these trucks

 

Many times the boots start to go bad what happens is the spark takes the path of least resistance, the grease tends to help insulate the boot and is less likely to allow the spark to jump to the head down in the hole, also makes the next removal easier. But the main purpose is to help insulate and contain the spark energy. many coils are repalced and realy the boot is the problem same as the old style coils when the wires failed. if there is the sligtest defect in the boot it will fire to the cylender head instead of to the tip of the plug. You may have had a boot stuck to the original plugs and when you pulled it off it made a little tear in the boot, look at the boots carefully, thay can be purchased seperatly.

 

I finally found the culprit , apparently when changing the plugs on the drivers side somehow I knocked off the fartherest back injector wire. I have no idea how I did this because I did'nt pull the wires off on the drivers side, must have happened while trying to change rear plug. I wish I would have noticed it before I pulled the plugs again & checked gap , applied dialectric grease ,and inspected boots but I am relieved that I have my truck back again. Thanks everyone for the responses.

 

That can happen the clip may have never been locked on and you knocked it off while working on it. The main thing is that you fixed it and putting the dielectric grease on is worth the problem of removing the coils again. It is done right and should last with out any problems. And now you are a modular plug expert!!!!!