If it only smokes after letting off the gas and then accelerating again might be valve guide worn out but sounds like oil leaks to me. Oil filters can leak if over tightened. Check your oil sending unit for leaking too. It is next to the oil filter. Pull the wire and see. If so easy fix, replace it, both for under $10. But it sounds bigger to me so read on.
Check the valve cover gasket! The rubber gasket shrinks over time and the screws will be loose if no one has even tightened them. Don't just tighten the screws, replace the gasket. It is only about $25 and easy to replace. Clean everything up well before you replace it. Tell tail sign is loose screws and oil and dirt all over the engine. On the front side it trickles down behind the exhaust manifold. That area at the head should be aluminum looking, not oil black and fury! The white smoke might be it burning off the exhaust pipe and header. FIX BEFORE YOU HAVE A FIRE!
Nissan 200SX 1.6 engine Valve Cover Removed on Flickr - Photo Sharing!
As stated above. Check the front crankshaft seal too.
CV Axles removed on Flickr - Photo Sharing!
Front crankshaft oil seal leak on Flickr - Photo Sharing!
Look for oil behind the harmonic balancer
Nissan 1.6L Timming marks on Flickr - Photo Sharing!
and on the air conditioning compressor and mount area under the car. It also blows around the engine to the firewall side
http://www.flickr.com/photos/[email protected]/2239904621/sizes/o/in/set-72157594347547443/
and into the passenger side wheel well. In bad cases the rear of the car will have dirty oil drops and splattering on the lower passenger side body under the car and on the trunk and rear bumper or more. The front seal only requires removal of the right front tire, plastic gravel shield, the fan belts and the harmonic balancer (The big double fan belt pulley on the bottom on the engine on passenger side. Use a puller, not a hammer or pry bar!) That big nut in the center may take a impact air wrench to loosen.
CV Axles removed on Flickr - Photo Sharing!
Sometimes I remove the oil pan and use a wedge of wood between a crankshaft counter balance on #1 cylinder and the engine block to keep it from turning if I have to get heavy with a breaker bar on the socket to get the nut loose. Careful on the placement of the wood in a thick area of the block. Don't want to crack the block or do damage. Your oil pan probably needs resealing anyway too. The RTV silicone sealant shrinks up too and needs redoing. The seal surface of the harmonic balancer will most likely be grooved where the worn out seal's pressure spring has been digging a groove in it. If it is replace it. Also note. The sealing surface is the outside edge of the raised area on the back side of the harmonic balancer, not the rear face of it. Look for grooving there and get a replacement that matches. Some Auto Parts Stores are selling a HB with that area not machined and smooth. Don't use it it will tear up your new seal and leak big time. Get the one that has the outside edge machined. It fits inside the seal not just up against it.
One curious thing about these leaks is they usually only happen at highway speeds so you don't usually see oil puddles all over the ground after you park. That makes a lot of people think it is burning the oil.
The link to my set of photos including those above. These are of 3 of my 200sx with the 1.6 l in and out of the car fixing similar leaks automatic and 5 speed.. Might help to see it here before you get started or have someone else fix it.
Twins + 1 - a set on Flickr