I also have a minor issue. The car runs and idles fine, but it will stumble or miss some times around 1500 to 2500 rpms coming down from 4000 or higher. It's weird and hard to figure out, I can't tell if it's a fuel issue or air issue because I have very little experiance with Z's. My first instinct when it happened at low end was injecters, so I ran cleaner and such and it seemed a bit better, but it may have just been the octane boost the cleaner added. At this point I lost faith in the plugs so I changed them and the wires, ran better but still had the issue. Next thought was the PCV valve so I changed it, didn't fix it. Now I'm contemplating the distributer cap, or coil. Before I keep changing pieces I was curious if anyone could give me some ways to trouble shoot this car better then guess and check
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