Had my plugs changed on my 07 Lariat 5.4L a month ago, drive it home park it and go overseas. 3 weeks later i come home start driving it and when i stop at a red light or let it sit idle i get a fume smell through the vents when i have the cabin temp control on. If i turn the AC on or recirculation it goes away or as soon as i start driving away from the redlight it is gone. I took it back to the garage that did it and asked them to check the torque on the plugs. They said it is good to go and they can't smell what i am smelling of course! I don't even want to think what a dealership would charge just to pull the damn thing into the garage. Any ideas? I want to tear into this thing myself but not sure where to start. Is it hard to get to the plugs to check the torque myself? Do i need a special wrench? It is a ford so i'm guessing yes i do need a special tool? Any help is greatly appreciated. i changed the plugs early because i know they are a pain in the butt now i got this stupid problem because i thought i was doing the right thing. Can't win with these trucks anymore.

 

Like a gas fume? Or exhaust fume? This could be something not related to the plugs. To check the torque you have to have a torque wrench. And you just pull the coils off and check them.

 

its like a gas fume, i have the torque wrench, do you just un bolt the coil and pull it off? It looks like there is one small bolt for every coil cover. If it is that easy i will attack it tomorrow

 

Yes remove the 7mm bolt that holds the coil pack on, remove the coil pack and check torque and tighten as needed. If it's a gas fume you might have a injector o-ring leaking, whoever changed your plugs shouldn't of had to take your fuel rail off but he might of. And if he did then it might not have seal right or he tore a o-ring. While your checking your plugs look around your injectors and see if it looks like they have been leaking or crank it and see if you see gas anywhere. Good luck

 

Not sure if this will help but I had the very same peoblem on my old chevy. It ended up being that I has a leak in the EVAP system.... so at a red light with no air circulating through out engine compartment it would smell really bad like gas. Then once accelerated it would go away. Same with the air as you explained. I would check the EVAP system (lines, purge valve, and canister) Most of the lines are hard and become brittle. I accidently cracked one changing plug wires, thus leaking fumes in the compartment. Hope this helps.

 

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if whoever installed your plugs was reputable whatsoever I would doubt it would be a loose plug because if your plug is loose enough to let out enough gas fumes to fill the cabin I would think the truck would be misfiring etc.

 

spark plugs are only tighten down to Inch-lbs... basically finger tight with another half turn.

The evap explanation above is most likely the issue.

 

check your injectors, they are easily bumped and easily missed, when putting in new plugs and COPs