Seems to run fine except in park or at a stop (chugs). Just replaced spark plugs. Engine light still on. EGR?, Fuel filter? Don't know. What other possible scenarios?

Seems to run fine except in park or at a stop (chugs). Just replaced spark plugs. Engine light still on. EGR?, Fuel filter? Don't know. What other possible scenarios?

Before doing anything else you need to check for codes since your check engine light is on.

Here is the procedure to retrieve codes:

The Check Engine Light (CEL) codes can be obtained without a trip to the shop or dealer, & without an expensive code reader. The Haynes manual for Mercury Villager/Nissan Quest covers this on page 6-4. To extract the stored codes:
1. Turn the ignition off
2. Unplug the diagnostic plug nearest the starter solenoid
3. Turn the ignition on but don't start the engine
4. Reference this diagram to determine which pins to jumper
5. Plug the jumper wire into the indicated pins in the plug & socket for exactly 2 seconds, no more, no less, and remove the jumper wire
6. The CEL should start blinking, a series of long flashes followed by a series of short flashes. It will repeat the cycle so don't worry about rushing back to the cockpit to get the codes. When the flash sequence repeats, count the number of blinks for the longer duration flashes, & count the number of blinks for the shorter flashes. This will give you the code, for example 12 long flashes followed by 5 short flashes is fault code "1205" which is the transmission "Line Pressure Solenoid" and/or circuit fault (96 & newer).

http://f1.grp.yahoofs.com/v1/IJyCSGpdr2YwgGny0f8M8fuF2fvgRURDAowWXxJndtASZHRGUL haqurqORjT1lX28we3eGFQiThnrzj9mBDfGfkAEjJ_WB8jxuM/Diagnostic%20connector%20location/nissan4.jpg

Post codes and we'll go from there.

i have a 95 villager too! i love it. it's the best american car i've ever purchased.

Auto Zone or Advance Auto will check the engine free for codes. If you haven't done it before I would do this.