I have a friend that has a 2002 6 speed with tst box 9 stage 2nd vp44, truck has been running great for a year but last night he told me that it has started to cut out it would be running good then all the sudden it just starts missing then straightens up and runs fine then it will do it again, I told him to take the box off and try it but he said it still does it. He didn't know how to run the codes and I tried to tell him but he didn't understand so I don't know if its trowing any or not but I told him I knew some people with more experience with the overvalved trucks and I would ask them what they thought, so have any of you running the tst had this problem?

 

to run the codes you have to cycle the key three times and then leave in the on position and if there are any code they should be displayed on the screen where the trip/odometer are.

 

Well, if the truck still has the problems with the TST taken out of the loop I wouldn't be thinking it had anything to do with the TST. The first thing I would do would be to check for any DTC's. Address them in order of when they first appeared. If there are any present the problem you describe sounds like it could be a P0336 (Crankshaft Position Sensor). There will be other ones as well, but they are because the CKP went bad! When mine went it wasn't as noticeable as your description, but similar. If there aren't any DTC's I would start looking at fuel pressure to the VP. I had one lift pump fail at 88,000 miles and I definitely experienced the problem you describe. How my VP lived until 159,000 miles after that I have no clue!

TST boxes for the '98.5-'02 trucks rarely have problems. Mine happened to be one of those rare ones. I replaced everything! VP44, IAT, MAP, CKP, CPS.... then, I finally threw it in a box and sent it to Mark. 2 weeks later I get a box back and it is a different serial number. Put it on and whoa!!! I got my juice back!!!