Hi! New member here, longtime lurker - first time poster. I have used these forums at length in diagnosing and correcting many problems, and find that it contains a wealth of information! Here's my deal - I have done a forum search and read most of the threads that contain issues like I am having, but I would like your advice on the next steps I should take. I have a 2005 5.4L. I have been getting the code p0420 intermittently for the past 2 years. It comes and goes and the outside temp seems to have something to do with it (could be psychosomatic). It happens frequently in the warmer months, but during the cold weather the CEL goes away and no codes. I had my spark plugs changed about two weeks ago. At the time, there was no engine light on and no code. I have been noticing a raw fuel smell in the cab since. I only smell it at idle, when stopped at a red light or stop sign. I took it back to the dealership that performed the work and they at first stated that they couldn't smell it. I waited a week and took it back, asking them to check to make sure the plugs were torqued appropriately, and that there were no other leaks. By this time, the engine light was back on (of course), reading the p0420 code. The dealership states that everything is fine plug-wise, and that the smell is related to the p0420 code. The thing is, I have been throwing that code for 2 years now and have never had the raw fuel smell. I foud it to be a little coincidental that the smell came about after the plug change, especially since that has happened to so many others. I also recently just learned of the extended warranty because of the sticking fuel injector issue. So I am at a loss as what to do. Could the smell be from loose plugs, a faulty injector, or truly a bad cat? The truck runs great, aside from the smell. Any thoughts would be greatly appreciated! Thanks!

 

Although it may seem like a coincident the fuel smell is most likely from a loose plug. They should all be check again and torqued to 28ft/lbs. As for the code it could be a bad cat. If under the 8/80k emissions warranty I would take it to the dealer have them check for a bad cat. They should fix for free if under the warranty and there is truly something wrong with the cats.

 

^^^ 25 ft lb on the 5.4 No anit-sieze on the threads

 

x2!...

 

While doing the plugs the injectors rail could have been remove and not reseated correctly....

Also your code could be a bad o2 sensor or bad sensor connector....check them out before changing the cat...

 

Thanks for the advice, everyone! An update - today while cruising at about 45 mph, I gently accelerated, and the truck shook like it was falling apart. It actually scared the passenger that was in the vehicle with me! I did have the skipping issue at this speed before the plugs were changed like some others have had, but nothing like what happened today. I hope I can get the tech with me on a test drive and I can replicate. I diagnose this as SARS - Sumpin' Ain't Right Syndrome. Looks like I'll be visiting the dealer for the 4th time in a week...

 

Might want to read this>>> https://www.f150online.com/forums/v8...ram-07m08.html

You never know.....that might be the cause....

 

Update: The shake got worse and the engine went into fail-safe. Took it to a different Ford dealer and they diagnosed a fouled plug on cylinder 1 and a bad throttle position sensor. Plug was replaced under warranty from the previous job, and I replaced the TPS sensor and gave the throttle body a good cleaning. All codes are now gone and the truck runs like brand new, smooth as silk. However, I can still smell the gas smell, only when the A/C is on fresh air. I personally checked the torque on the plugs and they are indeed tight. I also replaced some EVAP hoses that were a little funky, but there's that smell. I think I may just light a match...