Cold starts or hot starts? Any codes? Clean your TB and IACV along with performing any required maintenance like filters, plugs, etc.
Here's a link where you can download the procedure for checking, and only if nescacary, adjusting the idle speed, it may be a bit low. Good luck with the van, the VQ engine is even more bulletproof than the one in your '93
http://www.vq35de.com/ESM/Nissan/Quest/