I have been dealing with this issue for a couple of months now. My 2006 F150 with the 5.4 V8 crew cab ran well but as soon as she warmed up would idle rough when at a complete stop. Eventually the check engine light came on. I have taken the truck to 3 different mechanics. The first mechanic checked the codes and said that it came up P00420 and P430 but didn't think it was catalytic converters because he pressure checked them and they came back ok. So, he checked the fuel filter and said it was clogged so he replaced it. The truck ran better but it still idled rough when stopping. I had a friend recommend a mechanic he uses that he was quite pleased with so I decided to give him a try. He got the same codes but said that the cats checked out fine. He checked the air intake and said that he found leaves in the air intake so he cleaned it out and replaced the air filter. Truck ran fine but the idling issue persisted. So, I took it back to him and this time he said the codes read carbon build up and said that it needed a tune up that would cost about $500. Well, the next day he calls me up and tells me that he broke off three of the spark plugs and that it would cost an additional $30 an hour to extract. The next day he calls me and says that he was able to extract 2 of the plugs but couldn't get the third one out but he thought he could get it out. Well, the next day he calls me and says that he got it to back out 4 turns but the center of the plug fell into the cylinder and that it would take an additional 21 hours to tear down the motor to extract and clean the cylinder. Well, to make the story shorter he dinged me for $3900 which I raised total heck about it and he cut the bill to $3300. WOW! Anyway, the truck ran better but the idle issue still persists but now the truck seems to be running rough. I'm now into this for almost $4G... I finally decided to take it to the local Ford dealership to see what there mechanic would say. Well, I got a call today and they pulled the codes and guess what, P00430 and 420 and they want to replace the left side cats and O2 sensors for a whopping $2726. I just picked the truck up and paid them $140 for the diagnosis. I decided to take a look at the cats and the exhaust system and noticed that the front exhaust pipe that joins the cats to the muffler is crimped. Now, it almost looks like it was manufactured this way but most of the pipes I have ever dealt with were open. I would think that this would cause a restriction in the CO2 flow and cause back up into the cats, causing them to overheat and throw off the compression ratio. My question is, is it normal for this exhaust pipe to be crimped? Because if it isn't then I think I have found the main problem. My only thought is that if it has been this way for awhile then this could have created carbon build up in the cats and they would also need to be replaced. Help!

 

15x7 ford