F150 mystery

[90vert]

Sounds like either coils, injectors, or a clogged cat. You can test the injectors and coils by unplugging one at a time and seeing if it idles worse. I've also read about a way to check the coils with a timing light.

Either way the 5.4 3v is notorious for coil and plug problems which will result in a clogged cat. Maybe someone will chime in on a way to trouble shoot the cat.

[90vert]

Those should have a code if they are causing a problem, thought about a plugged cat/exhaust, may wanna check that. What you get on FP?

They won't always throw a code, sometimes you have to "work" to get it to trip the check engine light. You can do it by finding the rpm/gear/speed that the truck acts up in and holding it there until it finally trips the check engine light.

[warrjsmith]

So.... the mystery has been solved, it was 2 bad coils, now my truck is running great!!