I just had someone install a 5.9 to replace the ruined one in my 98 cargo van. The new engine has 54,000 on it, but has some running problems. the check engine light comes on intermittently. Once in a while, it'll start running choppy and lose power afer sitting at a light, andif I pull over andshut it off and then start it back up it runs fine again. It may be my imagination, but I almost think I hear a vacuum hiss when it's running rough. I already replaced both oxygen sensors. I know there are a huge number of possiblities but does anyone know of anything obvious that I should check? Someone told me that the spark plug wiring is a particular problem with these and that there is a way that Chrysler recomends routing them so they don't get near each other, but I haven't been able to find anything about it on the internet. I don't think that's it anyway because about half the time it runs fine.
By the way, when I go to the TSB list on this website, I can't figure out how to actually get to the tsb. Anybody know how to get them to actually read them?
thanks a lot,
Scott Scheffer

 

well i kinda of had a simular issue mine was my tranny and my check engine light only comes on when im really giving some gas ,and i got it to pass smog by disconecting then reconnecting the battery to clear codes and then driving 50 miles to get the computer to start reading again and go strait to the smog place and then you should be fine
you just need to see how long it will drive before it throws a code after you reset the computer

 

well take it somewhere and have the code read.
The symptoms sound like problems I have had with a bad O2 heater. Check and see if you have a separate 02 fuse under the hood or the wiring to the front 02 sensor.
Look for any disconnected vac lines and check your plenum gasket for internal vac leak.