Frankieramsook

03-350z. Good compression, good spark, good fuel. Misfires on cylinder 4 and 6. It has new plugs, new coils, new injectors, new intake manifold and gaskets, new valve cover and gaskets, new fuel pump. Would like any suggestions. Thank you.

MicVelo

Double check that the 4 and 6 wires aren't crossed. Very common due to the proximity of one another.

Jim Stephens

Could also be a vacuum leak. Check two things. Check to ensure all of the hoses are connected to the plenum. Run you fingers around the edges of the plenum and see if you hear or feel any leaks. Another way to do it is to take some saran wrap and put pieces around the plenum edges and then start up the engine. If it then runs well remove one piece at a time until it starts to misfire again. This will help you find the leak. I personally have experienced this problem of the misfire and it was caused by air being sucked in the plenum area (in my case I Missed a vacuum hose). Sometimes you can catch the rubber edging around the oil filler between the plenum halves. Watch this video until the end.