Chrysler Repair: when van is warm it bucks, cylinder number, engine controller

Question
i have basicly been driving the car and it started lightly bucking.
in oct i had the transmission rebuilt and today i did a tune up still bucks then i replaced the fuel pump  and it still bucks and stalls  

Answer
Hi Robert,
You didn't tell me the year and engine size/cylinder # in your van. If it is pre-'98 I would suggest that you do a readout of the engine controller to see if it has logged any fault codes that would give a clue as to what is going on. You can do it with your ignition key:
turn it: on-off-on-off-on and leave it on, doing this in an elapsed time of 5 seconds or less. the check engine light will remain "on" but then begin to flash, pause, flash, pause, etc. Count the number of flashes before each pause and keep track of the counts. The last two groups of flashes will always be 5 in number. Then repeat to make sure the counting you have done is accurate. Then group the numbers in pairs in the order of readout to form two-digit numbers which are the fault codes. The last such number will be 55 which is the code for "end of readout".
Then write me back with a follow-up question telling me the code numbers and I will respond with some ideas. Tell me the year and engine size and cylinder number of the van.
Roland