Nissan Repair: 87 Nissan D21 Rough Idle?, fuel delivery system, nissan d21

Question
QUESTION: Hello, I have an 87 D21 Hard-body and ever since I bought the truck it has had a very jumpy idle. I believe this is related to the vacuum system. Do you have any suggestions on possible problems? How can I check my vacuum system for possible leaks?
Much Appreciated,
Eric B.

ANSWER: Eric,

You can check the manifold vacuum with a vacuum gauge for specified vacuum at idle.  I would be looking at the fuel delivery system too to check for excess gas entering the system.  Also, inspect each hose and clamp and the intake gasket.  Lastly, replace the positive crankcase vent valve as these tend to gum up and mess with a steady idle.

---------- FOLLOW-UP ----------

QUESTION: Thank you. Also, Today when i started my truck in the cold weather it would idle rough and then the idle would drop and the engine would shut off. I have never has this happen to this truck in the cold before. Any suggestions? What types of things should I look for in the fuel delivery system?

Answer
Eric,

Make sure you have sufficient fuel pressure (change the fuel filter).  Also, if the sparkplugs have not been recently change (within a couple of years) change them. Need to check the idle circuit for proper operation that the circuit bumps up the idle when cold and steps down as the engine warms.  I would get a Haynes or Chilton manual to aid in the diagnostics of each.