I have a 98 Ford F150 4x4 with a 4.6 motor all of a sudden it won't idle. It runs fine but dies if you let off the pedal. I had the computer checked and got no error codes I am stumped any suggestions

1. I would replace the fuel filter, if it has not been changed within the past 30,000 miles.

2. Assuming your spark plugs are in good shape, I would focus on your igniter. O'Reilly Auto Parts and Autozone will test them for free.

It could be your fuel air mixture is wrong.
Or maybe for some reason your are losing eltricity to fuel injection

1. Replace fuel filter, if it hasn't been changed in 30,000 miles.
2. Replace spark plugs, if they haven't been changed lately. Replace Motorcraft platinum plugs every 50,000 miles, not 100,000 miles as suggested. Only use Motorcraft spark plugs.
3. Test/replace igniter and coil.