99 F150 Exaust temps HIGH

63cj5universal

Active Member
Joined
May 8, 2006
Location
Bailey, NC
My friend has a 1999 F150 4.6 liter (246,xxx miles)extended cab 4wd that is burning up. He has noticed that when splashing through puddles that steam has been rushing out from under the truck. This happens fast enough to fog the rear window before all of the water has hit the ground. He borrowed a lazer thermometer and checked around under the truck. After 10 miles of driving his muffler is 534 degrees. The lazer will not even read on the cats (one on each side of the oil pan) or the pipe near them. It appears he has located his problem. Now for the question.

To "punch out" his cats would not only be imoral, but ilegal. I understand this. BUT, if someone was to desire to do such a thing, would this work to cool things down? Maybee this friend has no desire to double the trucks value by redoing the exaust. Maybee the truck is nothing more than a farm truck. Maybee it will never have to pass emitions inspection. I just don't want the truck to burn up.
 
Don't kill the cats. It will kill your fuel economy because the O2 sensor readings will be wrong.

BTW - The O2 sensor is probably the problem. If the truck is running too lean then it will be really hot.

Have you hooked up a code scanner yet?
 
My Friend says the check engine light has been on for a while. By reading the codes he determined that one of the O2 sensor is slow to respond. Did not fix.
 
He is being told by a mechanic that if the truck was driven like this for a while (it was)the cats and the O2 sensor would be messed up. No need to fix the sensor without cat work.

Fuel mileage has decreased to 10 mpg.
 
I would tell your friend the problem is inside the circle on the front of the truck.

On a serious note. Do you plan on keeping/driving the truck long enough for the decreased fuel economy to equal the cost of fixing the exhaust and o2 sensor? If so, then I would say fix it. What fuel mileage would the truck get with the issues fixed.
 
If fixed 16 mpg. I understand weighing the cost of fixing it vs the cost in fuel, but eventually you have to make the hard choice to just put her out of her misery. The problem with sucking it up and fixing it right is the 246,xxx miles on it. This truck has had a hard life. Soon it will be needing a transmission rear seal, drivers side front axle, brakes all the way around, and a few other things. Just looking to nurse this thing along for a little while longer.

Oh yea....the circle on the front is what has kept this truck alive this long.
 
so to recap...
ce light comes on
friend ignores ce light...
CE light most likeley caused by bad o2 sensor.
bad O2 sensor causes A/F ratio to be screwed
screwe AF ratio screws up CAT
Proposed solution remove CAT....
got it

:lol:
 
It doesn't sound like the fuel economy could get much worse so I say remove the cats and keep her cool.
 
If you gut the cats and don't fix the O2 sensor problem, then it will likely live a short and painful life. Running lean is hard on the motor, and will cause it to burn out the pistons and blow head gaskets. Running rich is hard on the motor, and will cause it to wash out the cylinder walls, and eventually, crank bearings. Fix it, and it may live another 100k hard miles or more. You make the choice, although it sounds like it's already been made. You came here looking for confirmation of your assumptions, but haven't found it.
 
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