Coil Pack/Injector Malfunction Help Please!

[Chrisseizure]

Hey there guys, so I am completely new to this forum, but have been using it quite a bit for info on how to put my 1990 Nissan 300zx NA 2+0 back together. I must say, this forum is the absolute BEST I have visited, and no other site compares, so thank you guys! Please bare with me as I will try to explain my problem to the best of my ability

So, I recently dropped in my motor, wired her all up, and when I started her up, I noticed she was running rough. I figured it may have been a misfire, so I began pulling the connectors from the coil packs to see if there would be a change in idle. Cylinders 1,2,3, & 5 were firing correctly, however cylinders 4&6 both had no change in idle. I replaced the coil packs, as I have extras, still nothing.

So then I pulled the intake manifold, replaced the injectors in cylinders 4 and 6, re installed the manifold. Cylinder 6 fires, YAY! but cylinder 4, and now cylinder 1 aren't firing. Tried replacing the coil packs again, nothing. I've cleaned the connectors from corrosion and spent time making sure everything is hooked up properly. Just have no idea why cylinder 1 is now not firing, yet cylinder 6 works fine now after an injector replacement.

Cylinder 1 coil pack is getting spark, so Could it be that the injector just went bad? Also, any idea why cylinder 4 is still not firing?

Thanks guys, hope I explained myself well enough

[Chrisseizure]

Just played around with the car a bit. The coil packs for cylinder 1 & 4 aren't getting spark. What confuses me, is how cylinder 1 was just working fine before I pulled off the intake manifold and then re connected it. All my plugs are in the correct spots. I am also still unsure as to why cylinder 4 has no spark.

[Titek]

Read the post at the top "Dead Cylinder? Can't figure out why? Read Me! (S2 PTU Test)". Sounds like a PTU problem.

[DCaff300ZX]

Good call Titek, PO check your two PTU harness connectors as they also are very prone to corrosion and can cause misfire issues. Jostling it during removal of the plenum possibly aggravated it, also check the CTS sensors on the coolant hard tube in front of the motor and CAS connector for corrosion.
Moving the PTU and harness off of the front of the motor and to under the front cover or lower is a common mod, helpful for a better environment for the PTU and harness. I myself have also replaced the lower PTU harness with an upgraded one from Z1 that is weatherproof, unlike OEM recall replacement harness connector.
I'd also carefully check your injector connectors as the #6 in my NA used to be a real b#@*ch to get seated all the way, what with the injector/fuel line/coil pack connector clutter there under the balance tube, I get fuel leaks there often since everything there is so tight and hard to access...bottom line is I have found things during these types of checks that solve problems with a surprise oversight or discovery.
Let us know how these tests go!