speedtrapp

Hi guys have a question maby you can help My 02 f150 supercab lariat 5.4 auto 4x4 73K, my mpg has gone to 10-12mpg. it was 15 or better. resently a coil went and before I realized it I think I overheated the converter, I drove it maby 20 miles and when i stopped it was glowing red like the sun! The next day I changed the bad coil and put in all new plugs air filter fuel filter and oil. and now my MPG is horriable, could the converter be playing a role in this? there is no back pressure problem the truck runs great no engine codes, but there seams to be a noise comming from the inside if the converter. any ideas.I put in ford plugs but are there any better ones? thanks for the help

otto457

I'd say if the cats were red hot there is a 99 percent chance there clogged. They melted. You have fix the cause, but your cats are probably ruined. Your forward O2's are spent, this is probably the cause. You might not get a DTC for them if their burnt and mis-reading.
To correct, I would start with new cats (Magnaflow 94106) and forward OEM O2 sensors so the A/F ratio's are set correctly. Make sure everything else is up to par, - like a squeaky clean MAF sensor. Do you have any other modifications to the vehicle? I ask this because anything else that will make it run rich can do this too (ie bad tune, etc).

speedtrapp

no the truck is dead stock. The bad coil was on the left bank( sitting inside truck) #7 cyl I think, so when I looked under the truck the converter under the driver side was only glowing, can I get away with replacing one or I should do both, I dont know if this truck is true dual exhaust or not it is the original exhaust though Thanks for the help this is a great site

otto457

Ok I follow better now. The bad coil caused fuel to go through the cylinder and onto the cat. Fuel burned in cat=red hot. Replace that front cat and O2 sensor. I'd take a inspection camera and look at the second cat while the front one is off to see if it is clogged too.

speedtrapp

OK are thoses cats a direct replacement or will i have to cut them in, will they change the sound ? I like to keep a low profile I am not looking to bring any attention to the truck. I see they are very cheap but looking on crap bay I see some for 300-400 is this because the magaflow are a universal fit type again thanks for the help

otto457

Those cats you would have to cut them in to fit. Summit has direct fit ones that are $300+. Either way it will change the sound slightly but shouldn't be too bad volume wise.

speedtrapp

Thanks otto I think I will just buy a replacement I looked under the truck today and it looks stright foward, remove the engine pipe flange nuts and U bolt hanger, I would go with a replacement but with my luck the upper cat will be toast too, I see they are around 300+ but it is what it is, thanks for the help