i have a 99 f150 that i just got it seems to run ok when cold but as soon as it warms up it wont idle and there are flames coming out of the exhaust I'm kinda at a loss just wondering if anyone has some feedback that might help

 

Leaking fuel injectors.

 

I'll check into that thanks hopefully that is the issue

 

You need to look at other things too - such as a leaky fuel pressure regulator (pull the vacuum line off it with the engine off and see if fuel drips out of it), spark plugs, wires/coils, compression, etc. Check for OBD2 codes.

If you have flames coming out the exhaust, your cats are either shot/plugged or will be soon.

 

The the truck has had some work done to it it was change from a 4.6 to a 5.4 also has a manual transmission not an automatic so I was just curious as to what are some of the things to look at to see why it only seems like it's running on 4 cylinders when it's cold after it warms up it starts sounding better but that's when it stops idling and starts shooting flames