Nissan Repair: misfire, mufler, distrubutor

Question
Hi Von

        I am very sorry for bothering you with so many questions .... i know you are the best ....
 i have a 1990 maxima 5 speed .. i worte last week that  its loosing pickup in th intial stages and there was a debate  on ... distrubutor and fuel filter  and so on ... suddenly it started running fine i drove about 150 miles one way and it was just fine BTW it has 170 k on it ... yesterday while driving back from work ....
it started to show the same symptoms this time its worse ...... ther is a misfire in the idle ... a constant one not  droping and pickin up and sooo on .....

  there is rough ideling sound comming out of the muffler ( mufler and the whole pipe is 1 yr old..)
engine is quite as ever so good ... it still drives 75 m/hr with no problems but the rough idle still remains .....

the Rpm shows no variation .... there is a miss some where ......it dosent fire properly ..  this si a old car and i cant spare more than 500$ on it to fix ....  i know you are the best .. please advise..

thanks in advance .
Raj  

Answer
Raj,

It sounds like you have a bad sparkplug or wire.  If it idles bad and you can hear the miss out the tailpipe I would check the plugs, wires, cap and rotor before I did anything else and that can be done for around $100 bucks if you install yourself.