# Idling and Speedometer questions



## DuoWing (Jul 17, 2005)

I've been looking at some Nissan 300ZX's recently. I found an 85' 300ZX N/A. It has 135k miles on it. It's stock red paint in pretty good condition, interior is good. The guy tells me that last summer he had a a big tune up done to it. Timing belt changed, etc. He also said that while the timing belt was being changed he had them do head work on it, I guess port and polish, etc. He had a stainless steel exhaust put on the car. He says he's never driven it in winter, the underbody does look like it has some rust, but that's common still for Ohio. Everything works on the car and it doesn't leak.

So we started the car up as it was sitting there idling, it seems to kinda vibrate alittle more than I would have expected, I'm not sure if this is abnormal or not. I've really only seen 3 different Z31's up close. All N/A's. The other two didn't really vibrate. He says due to the port and polish, the exhaust and some of the other things done to the car that is has lost some power in the lower RPM ranges, but has gained more power in the higher ranges. I don't know if this would attribute to the vibrating, also the bigger exhaust piping, would that contribute? Anyway the idle seemed to be around 600-700 RPMs which is about normal and the tach was displaying a smooth idle.

So we get the car going and I took it out for a test drive, from what I could tell it was shifting smoothly, and the brakes were pretty good as well. He said he had newer brakes put on recently and it has a newer clutch. Anyway we get driving and after awhile I realize that the Speedometer doesn't work. The speedometer just shows a constant 0 mph. He said this broke very recently and he said this is not a big or expensive thing to fix. The odometer hasn't worked either, so is this just a cable or is the Speedometer and odometer actually broken?

As far as I could tell the vibrating of the car and the the Speedometer were about the biggest problems. So what I want to know, is this vibration unusual or anything to really worry about if I buy the car? I was wondering if the speedometer would be hard to fix myself or would I be better off going to a shop?

Now the best part. I already have an 85 300ZX N/A that has some problems, but runs. It has a working Speedometer and brand new tires. I got the car for free so would I be able to use the parts from that to fix the Speedometer? 

What I want to know is do you guys think this car is a good buy? He's asking about $2500 for it. I was curious to see what you guys think it's worth, but I just wanted to run the vibration and speedo problems past you guys before I make my decision.


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## Zen31ZR (Mar 24, 2004)

My 85 turbo had a very lumpy _sounding_ idle, with no exhaust on it, but idled very smooth. It also idled at 500 rpm. Vibration could be caused by just about anything, unfortunately, it's very hard to diagnose by remote. Could be a vacuum leak, could be a bad plug wire, could even be a missing or loose bolt on the clutch assembly.

As far as the speedo goes, hopefully it's just the cable.


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## DuoWing (Jul 17, 2005)

So essentially the vibration isn't a big thing to worry about? As for the speedo, if I were to have a shop fix it, would that be an expensive fix?


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## Zen31ZR (Mar 24, 2004)

DuoWing said:


> So essentially the vibration isn't a big thing to worry about? As for the speedo, if I were to have a shop fix it, would that be an expensive fix?


Does the vibration increase with rpm? Or does it go away. Generally, the higher up in the rev range the vibration persists, the better chance of it being a major problem. 

As far as the speedo goes, probably not too expensive. Cable is pretty easy to replace, and I would suggest doing it yourself. A shop could lie to you and tell you the speed sensor is out (much more expensive part), and what choice do you have but to beleive them.


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## DuoWing (Jul 17, 2005)

the vibration actually only seemed to occur when it was idling. As I was driving it was fine. It wasn't even like violent vibration, it was just more than I was used to on a car. Or at least used to with a 300zx.


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