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81 280ZX N/A speedometer issue and slight hesitation


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New to the Ratsun forum and new to Z ownership as well. I bought my Z for $800 bucks and it passed smog with a tune up and replacing some vacuum and fuel lines. I know I need a cold start valve but that can wait. The lady who owned this was the original owner and took pretty good care of it until she parked it about 6 years ago. It even ran on the old gas that was in the tank when we fired her up. 

 

When I got the car the speedo started out just being jumpy but then it moved on to spinning around which caused the needle to snap. My odometer still worked fine at that point. I have replaced the speedometer cable but when I did upon inspecting the back of the gauge cluster, I found where the shorty speedo cable attaches is loose at the back of the instrument cluster. I have also managed to lose my odometer since I have replaced the cable. 

 

I was just wondering if this means I need a new speedometer itself or if there is something I can do to repair the existing speedometer. I'm trying to not put a ton of money into her at the moment as I am trying to save to fix my Mustang and this is a driver for now. But I have been pleasantly surprised owning this as my first Japanese car. It's easy to work on and fun to drive. Any help would be appreciated with the speedo.

 

Also, the Z hesitates/ stumbles slightly under acceleration from a stop and it hesitates a bit when I hit around 3500 RPM. Could this just be some plugged injectors or could it be another underlying issue?

 

When I did the tune up on the car I did plugs, wires, cap, rotor, vacuum and fuel lines, fuel filter, air filter, adjusted the valves, and replaced the valve cover gasket. Other than that I scrubbed the hell out of the original paint and interior and it cleaned up nice.

 

 

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Speedometer needle snapped off ?? or just stopped working?

 

Jumping speedo needle is a dry or binding speedometer cable. It's basically a long tightly coiled spring that can momentarily catch, storing up energy and then releasing making the needle jump.

 

If loose on the cluster end you may have the wrong cable. I believe the zx cable screws onto the gauge cluster but around that time some Nissans like the 720 truck clipped on. Your new one should look like you old one and may just need the correct one.

 

The speedometer cable can be a bit longer than needed but should never be too short. There must be no sharp bends in it either.

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I get how a speedometer cable operates and it can't bend or bind. I know it is the correct cable because I compared it to the old one before I installed the new. The 280ZX has a shorty speedo cable that comes off the cluster that then attaches to the longer speedo cable that goes to the tranny. This also isn't the first time I've worked on cars I'm just unfamiliar with these cars. 

 

The needle snapped but that's irrelevant to me at this point. I'm just trying to get my speedo and odometer operational. Where the shorty speedo cable attaches to the cluster is the part that's loose. I didn't remove the cluster completely out of the car as I'm still driving it and it is my only operational vehicle. From what I saw behind the cluster is the attachment for the shorty speedo but it does not appear to bolt on to the back. It may have been pressed in but I'm not 100% and that is what I'm trying to figure out. I know that once the back of the gauge is correctly put together the speedo and odometer will operate. The needle still moves by playing with the back of the gauge.

 

And thanks for the quick response.

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Never knew this before! Just checked and the short one is 25050-P8220 and 345mm or 13.5" long. The longer one is 25051-P7100 and 2050mm or 80.7 inches.  Maybe this is a way to join an earlier screw on to a later clip on??? How do they join together???

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There's a quick connect style with a quarter turn retainer on the shorty to the gauge and then the two cables have a male(shorty) connector to a female on the long connector. I still need to find out how the back of the gauge is supposed to be because both cables spin freely.

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As for the hesitation, check injectors and then check fuel pressure regulator!  Pop off the injector clips while running one at a time, see if no change on one or more cylinders.

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