It runs, but sputters badly

Here's the problem. A buddy of mine just bought a 1991 Nissan Maxima with the VG30E (I know I wanted to see the VG30DE too) but anyways that is not the problem. The problem is that when it rains the car has a hard time running. Now in the dry it is good. Also when the car is driven hard in the rain it seems to clear up, and afterwards it runs fine, but as soon as you shut it off, and turn it back on, it sputters, and is really boggie, then you drive it hard for a few seconds, and it clears up again. I have no idea what is wrong, I was hoping that this may have happened to some of the SE V6 guys here, and that there is a fix for it.

Any help would be great, thanks 8)

Sounds like he might have a bad sensor somewhere, or possibly a bad ground on the main EFI harness, or a wire shorting somewhere. Try running an ECU diagnostic. Could be Throttle Position Sensor, Cylinder Head Temp Sensor, O2 Sensor, AFM, Crank Angle Sensor, etc. All of those sensors can do very odd things, and they don't always exhibit the same problems when they go bad. It's VERY odd that it would only happen in the wet.

Is he running a cone filter or anything like that? Sometimes if they're not sealed well on the intake or if it's a badly designed filter moisture can get through and reach the hot wire in the MAF, which causes it to go ape s**t since it's measuring temperature change.

could it possibly be that the distributor has a crack in it and gets moisture in it?.. i mean that could make it run like crap..

The car is completley stock, and I too found it really odd.

maybe..theres a leak (or blockage) in the intake, causing moisture to get into the cylinders..

Yesterday we took the whole intake apart, including the TB, and cleaned everything. Then we put a new fuel filter on it, and put everything back together just before it started to rain. I will probably find out today if it is any better. We are also seriously thinking about changing the O2 sensor, and I was wondering if there are two in the VG cars. We can see one at the front, but haven't looked for a second...8)

The VG only has one 02 sensor. (87 anyway, Cali models may be different, but I don't think so) Also, rain will not cause an internittent failure in the 02 sensor. Rain may cause an intermittent failure in the circuit. Don't buy a sensor until you have checked the circuit. ECU self diag (mode 3) is a good (read: quick) way to do this. The ECU will tell you if there is (or has been for the last 50 starts) a short circuit on any of the "critical" sensor circuits. How nice.

Oh the Fuel filter solved the problem, but we just wanted to change the 02 because the thing "enjoys gasoline". Plus so far we have found two O2's, and still counting...Stupid 91 Maxima...8)