Several weeks ago I washed my engine, something I've done many times before. later the engine would spit rapidly out out the blue, water in fuel light came on, code came up for heater grid low voltage, and TPS/APPS, connection was loose on intake heater grid. Figured maybe water got in connections, so I put dielectric grease on all connectors. Happened intermittently after that and pulled the APPS/TPS code, so found a module from Freightliner , (I made the timbo wire mod previously), still get the rapid "spitting" it seems after fueling a low tank, have added Howes Fuel lubricator that's supposed to remove water. Ran it till Fuel light came on, and poured a whole bottle in, gonna run that till I'm almost dead empty, see what it does. Any suggestions welcome.

Are you getting fuel from a farm tank or similar? Really common out here the farm tank gather water and all kind of issues can come with it. 

 

Check with your local fuel station to see if they run water blocking filters on their pumps. I know my local Chevron does have water blocking filters.

 

Check for air leaks as well. I just got done with @Jthorinjectors went down to the dump to ditch the trash in the bed. We had less than 1/4 tank and got up on the top of the pad short climb and it was lopey. Shut it down and looked around nothing leaking out or anything. Dump the trash went to start and it lost prime (long hard start). Ran home grab  my wallet and dropped $40 in the front tank problem is gone. Idle fine every stop. So he's got a sucking air leak either on top with a rotten rubber hose or bad pickup in the tank. 

Mike, I get fuel a various location across the country, usually at a Walmart/grocery store fuel station. Really bucks though when it does it.