From another board.
My wife and I had Nissan Quest van that developed an erratic drive-ability issue. Sometimes it would run great and others it would stumble, go dead, skip etc. I figured it was beyond my skill set to diagnose so I sent it to a independent shop that has served me well for many years. They diagnosed a fuel pump issue so they dropped the tank and replaced it. $300.00 or so. This did not solve the issue and suggested that I needed to take it to a Nissan dealer to check out the ECM. They said the ECM was defective and they managed to find me a used one-I think this ran like $1500.00 with the labor and all. I picked the van up an it seemed to do well for a few days but then the same issues we had at the beginning started happening. Disgusted, I started searching the internet for possible solutions and stumbled upon a thread about the top bearing in the distributor failing on other Nissan vehicles with the same V6 engine. Sure enough, I pulled the guts out of my distributor and found that the top bearing had completely come apart with the top seal gone and only half the balls remaining. I went to a local electric motor repair shop and bought a new bearing that cost me less than $5.00 and made the van drive like new.