First of all...the torque converter fails to lock during highway cruise until I'm going down the road like 5 miles after warmup...then it works fine. Is there some sort of TCC solenoid that might be going bad? This only happens when I first start the truck up, drive it around town, then hit the highway.

Secondly, when I go to cold start the truck, it sometimes "stumbles" really bad ALMOST to the point of it dying but it doesn't. It will start and fire, stumble like it doesn't want to run, and then the RPMs jump up and it runs and idles smooth as glass. What's up with that? This is a 4.6 with 59K miles on it.

 

I don't know about the converter. I'd guess its your iac valve causing the start problems. I've put 2 iac valves on my 97 in 120,000 miles. They go bad & really mess with the idle.

 

There is a TCC that controls the TC lock up. They are cheap ~25 dollars and you can do it with pan removed. Lots of the TC have shudder , and a flush sometimes fixes that.

 

I second the IAC.

 

Hello, my dad has described a similar problem with his 97 F250 light duty 5.4 . He says that after cold start up it takes longer for the trans to shift into over drive. After warm it shifts into over drive normal. Could it be that the converter is not locking until warm and he thinks it is not shifting into over drive?