I got a 92 6.2 diesel and in the cold it will start and idle great but after i drive it for at 1/4 mile or so it will start surging and at about 50-55 mph it will start jerking and jolting back and forth. Anybody know what is wrong?
Thanks, Scott  

Scott I don't know what your problem is but i'm pretty sure we have the same one. If you read my problem called missing jerking i'm guessing you'll see some similarities. I just wrote to say that if you have any luck with this please give me a shout out, if I do i'll do the same. Sorry I have no answers but i'm on the hunt as well. Let me ask you this, if you hold the gas down will it come up to speed just fine until it get to the speed the pedal is set at then it just starts cutting out and jerking hard? Another thing to think about scott if you have an automatic i'm pretty sure this problem cost me a tranny a couple weeks ago.  

sounds like your HPCA (housing pressure cold advance) is not shutting off. could be the "cold advance switch" which is screwed into the passenger side cylinder head in the lower rear corner. When you start up cold it senses the temp and changes the timing slightly for warmup and is supposed to shut off and if it doesnt will cause surging and rough operation. hope this helps