Black smoke from exhaust,no idle in warm temps-97 Nissan 2WD 2.4L

White smoke indicates water going through your engine or condensation in your exhaust. If it is a lot of smoke you probably have a small leak in your head gasket that seals back up as the engine warms and the materials expand. It will get worse as time goes on. If it's just a little smoke that doesn't last long it's probably condensation in your exhaust, especially if it's cold outside. Condensation is caused by the air cooling down in your exhaust after you shut down the engine.

1991 Nissan/Datsun Truck D21 Truck 2WD 3.0L FI 6cyl

The Ignition Timing
15 Degrees Before top dead center*Warm idle speed 750 RPM*Transmission in neutral (Parking brake engaged)*All accessories off.

1991 Nissan/Datsun Truck D21 Truck 2WD 2.4L FI 4cyl

The Ignition Timing
10 Degrees Before top dead center*Warm idle speed 800 RPM*Transmission in neutral (Parking brake engaged)*All accessories off.

You may notice when fired up blue smoke that fades when warm, oilrings worn..

Always replace with a new or working used one. I have never heard of rebuilding a MAF sensor!!

I just had a similar situation. The truck would run fine and then the Service Engine Soon light would start blinking and the truck would go into "limp" mode. It would eventually stall. Strangley though, if I turned the key over and then restarted it, it would start right up and run again. It ended up being the IPDM (Intelligent Power Distribution Module) that was bad. It cost me $520 to replace it.

it soubds like you have a vacum leak problem listen for a "his" with the engine running. you may want to take apiece of hose @2-3ft long put one end at you ear and probe arround the top of the engine arrount the intake manafold and any hoses when you find the his find wher it goes and replace repair the hose. it may also be your pcvvalve thst is stuck it willcome out of the top of your valve cover and plug right the intake hose right before the throttle body

It's time for a Italian tune up!

The blue smoke can be one of two thing.

oil drop from the valve stem (from engine head to cyclinders)
or
diesel soot collect inside the exhaust system.

===
I will take a 5-10 minutes high rpm (not redline) ran on the highway.
Pay close attention to the rear view mirror and look for black diesel soot.
=== I will use Diesel Cleen or similar product to condition the fuel. (keep moisture down)
Use the recommended amount of SEAFOAM oil additive to condition the valve stem seal/rubber parts.

I can not rule out excessive blown by.
Can you get a diesel compression tester?
When was the last valve adjustment?

Please post the actual odometer on the engine and I will follow up on it.

CATALYTIC CONVERTER MAYBE! BE MY GUESS AND IT ONLY HELPS THE TRUCK TO HAVE IT CHANGED!

did you check for vacuum leaks probably a vacuum hose thats been knocked off or eroded and needs to be replaced.

Puffing white smoke is a sign of a blown head gasket. Coolant is getting into the cylinders.