I posted this on a forum on another site and after a week I haven't gotten any advice so I figured I'd try here.

Ok folks, I've been having a problem with the truck and hopefully i can get some decent suggestions if not a fix action from all the knowledgeable people on this site.

Ok the details, 2006 F-150 5.4, 110k miles. Transmission rebuilt by a reputable shop 4k miles ago.

Now here is the problem.

After the truck is warmed up, it will act like it wants to stall when in drive at low speeds and in reverse at all times. If I put it in park or neutral it will smooth out in 10-20 seconds with no action from me or sometimes I can get it to smooth out by revving while in park or neutral. Going down the road it works like a champ, shifts fine, sounds great and is even fine downshifting when slowing to a stop. It is even fine when starting out again assuming i'm accelerating and it gets out of first or second gear. If I am going slow ie. parking lot or something the engine will shudder. I was on vacation the week after the rebuild and it was acting up and took it to a shop and they put it on a scanner and we drove it around. The guy couldn't figure out the problem but the scanner did show multiple misfires accross all cylinders while it was going on.

Now I could take it to the shop since the repairs are under warranty and that will most likely happen but I'm at work right now and have the time to post in the forum for suggestions. I have been told by a mechaninc buddy that it sounds like the torque converter is trying to lock up at idle but doesn't understand why but he's not positive because he hasn't seen the truck I just explained the problem to him. I had the codes read at autozone and got P0442 P0420 and P0340. Not sure if these are just symptoms of another problem though<!-- google_ad_section_end -->

Any ideas? I'm open to answering questions about the symptoms also if that will give anyone any ideas.

Thanks