6th piston not firing. help.

[yeskaexpress]

hi i have a 90 300zx na and im having problems with the 6th piston not firing.ive tried replacing the injector with a new one and injector pigtail connector because it looked a little green also a new spark plug but im pretty sure im getting spark. any suggestions would be helpful. thanks

[robomatic12]

Might I ask how you have figured out that the 6th cylinder is not firing?

What did you replace the injector with...oem nissan new or used? Use a multimeter to check the resistance between 2 terminals... should be around 11-13ohms.

What spark plugs are you using? These engines are picky about the plugs, they will run with anything somewhat correct but you can get problems down the line with hesitation if your using the wrong plugs.

Do you have the series 1 or series 2 PTU. PTU is located on the left side timing belt cover if your looking at the engine. The old version has a metal heatsink on it, new one just looks plastic.

Check all connectors especially for injector, coilpack, ptu, cas for corrosion and clean.

[yeskaexpress]

Well I checked the 6th piston by removin the coil pack harness and the only one that doesn't drop in rpm is the 6th piston.I did not replace it with an oem nissan one just a rebuilt one from the local auto parts store. I tried checking the ohms but I think my multimeter is messed up cuz I couldn't get a readin on any of the injectors it would just go up and down. I had an NGK sparkplug but I replaced it with a new random platinum one. Im not quite sure on the ptu I think its all plastic but not sure because im not home and I checked all connection except the CAS where is that at?

[robomatic12]

CAS is the crank angle sensor found on the front right of the engine, exhaust cam.

Sounds like you have the series 2 PTU.