Nissan Repair: Valve rattle and miss, hardbody pickup, cam follower

Question
I own a 1994 hardbody pickup with a 3.0 liter v6 and a 5 speed its a 4 wheel drive just to mention :) soo neways i have bought the truck used and about a month ago it started having a rattle like valve train rattle and it was only when i started it up when it was cold in the morning. Also when i would put it under a load but it gradually got worse and it would rattle quite a bit but clear up at high rpm. But just yesterday on the home from work when i took off kinda fast form a stop sign to get out infront of traffic the truck was missing real bad and rattle was extensivly worse and constant unlike it was before. When i got home i popped the hood and was listening at idle it would run clear then it would miss  a couple times. But when it missed a valve would tap im puzzled. I dunno maybe its the vavle train gone bad or a timing belt needin replaced and it slipped and jumped time but if you kno for sure plz help ! I have no expericnce with nissans only chevy's

                thanks A.j.

Answer
What is the oil pressure on the engine?  If the oil pressure is fine they you are probably correct that you have valve train trouble.  First, check the timing to see that the engine is set correctly.  Next, remove the plastic covers that cover the top of the timing belt.  Spin the engine around to top dead center and see if it has jumped a tooth.  It is a possibility.  If it has replace the belt.  But, I would think you have a stuck cam follower.  It is sort of like a lifter.  But, since you have overhead cams the dampner is under the valve cover and not in the valley like you are used to on Chevy engines.  It sounds like the oil gallery is blocked or you have a bad valve spring.  Check it out in the order I described and if the belt has not jumped you shuld take the valve cover off and see where the problem is.  Also, when you remove the plugs, as part of the valve cover removal process you should see which cylinder is the one with a problem.  Now, there is another avenue to the problem.  If the distrubutor is not firing correctly it can give the impression that you have valve trouble and since you do say you have a miss when you hear the noise you might have a bad distributor and oil will be getting into the bottom of the distributor with a bad seal.  The optical sensor will get oil on it intermittently and make the engine miss.