240sx Speedo is off?

[Guest Rane]

I just bought an Auto 240sx for a beater :-p. And the speedo gets off at higher speeds, its accurate till like 55ish and once you get higher it will accelerate fine but the speedometor goes down really slow and when you get back on the gas it picks up from where it slowed down to. So if I'm going 65 and let off I can drop to like 55ish but the speedo will stay at 60 and when I get back on it it will go up from 60 and get me way off speed. So It says I'm doing like 75 and I'm really doing 60. Anyone know anything about this? It also has a faint rattle when I get on the gas, but when I'm not accelerating I can't hear it. If anyone has any info let me know.

[Guest doggunracing]

Rattle is probably exhaust heatshield, just rip it off.

[Kevin R.]

I bet the speedometer problem is your speed sensor. I remember we changed one in my neighbors Civic.

 

 

Sounds like yours is just dirty or is starting to fail. His would work like that sometimes and other times it would not work at all. It would just be at 0 all the time.

 

Might not be the problem, just a guess.

[Guest wigsite]

I've had bad speedo cables that gave that same symptom. Where is the rattle coming from. It might be frayed wires on the speedo cable rubbing when its spinning quicker at acceleration.

[Dave1647545494]

if its electronic start with sensor if its mechanical change the cable if niether of those fixes it the guage is toast