Nissan Repair: 1992 nissan stanza, 1992 nissan stanza, nissan stanza

Question
my car is running rough, it sounds like it is misfiring.  we changed the plugs, wires, distributor cap, rotor and pcv valve.  it only has 70,000 miles on it. we tried a compression test we got readings of 120, 150, 120 & 150 for a 4 cylinder.  we would like to know how high the compression range should be.  thank you

Answer
Brian,

You are a little out of range since the books say you should be within ten percent on the compression from one cylinder to the next.  I like 140 psi myself.  So, even though the compression is down on two cylinders you might be ok.  I would pour a teaspoon of oil down each cylinder where the sparkplug goes and do another compression test and see if it is the rings or the valves.  If the compression raises then you know the rings are the culpret.   If the compression is the same then it is the valves.  But, I do not think compression this far out is going to make the engine run bad.  I would be looking at the injectors, fuel pressure and the egr valve to see that they are doing their job.  Get a Haynes Manual and check the fuel pressure and then actuate the EGR valve to see if it is slightly stuck open.  If you open it at idle the car will run rough and die.  That sounds like a place to start and if you need more help let me know.