I have a 1997 F-250 with a 460. All of a sudden one day it started running funny. at low rpms when it is lugging or you push the throttle in so far, it starts spitting and sputtering. but if you get the rpms up it purrs like a kitten. also it only does it once its warmed up. when its cold it runs like a champ. and also the check engine light is not on. ive checked the basics and cant find a problem, but wanted to get some opinions before I start replacing sensors or anything. Any ideas for this, please let me know. Thanks.

 

this could possibly be your throttle position sensor. i had a similar problem.

 

Could be fuel related, check your fuel filters.

D

 

Thanks for the opinions. I put a new fuel filter on the truck today and it didn't seem to help. I am thinking possibly a weak fuel pump or throttle position sensor. your thoughts?

 

check the fuel pressure as a start.

 

How about checking for engine codes.

Just because your MIL is not on, does not mean you have no codes.

Also, give this site a read, as it lists Engine management components and their symptoms when going bad.

http://oldfuelinjection.com/

 

Could be something as simple as a bad coil that is partially shorting out when it gets hot. The ignition module is another potential culprit that should be looked at.