[iixiom]

So throughout the winter my del sol has been running strong at 140k+ miles. As of about 2 months ago my speedometer has been whack. Any idea what may cause the gauge to show speed incorrectly? I have figured it is off by about 10MPH from 0 to about 35. past 35 its hit or miss. Im sure im not doing 40mph on the highway in 5th gear and 3500 RPM! Any help appreciated. Thanks!

 

[Kabooki]

Assuming stock wheels?

 

[iixiom]

Correct. The entire car is bone stock. Am i going to need a new gauge or something along those lines?

 

[mattliston]

your VSS might be bad.

Have you ever taken the gauges out, maybe to replace a bulb or something? Possibility of knocking something loose

 

[iixiom]

i have taken the gauges out to replace the bulbs with a different color. but that was a long time before this started happening.

 

[ryry702]

i had something like that. i replaced the speedometer and it fixed the problem. good luck

 

[Serj22]

Every speedometer needs to be calibrated after about 2 years. After that it is usually incorrect. We have to calibrate and dictate actual speeds on all our cars at the station, I.E.- if the speedo says 70, you're really doing 65. That sort of thing. The wheel spin is what's measured, that's why kabooki asked if you had stock wheels, change the wheels, it changes the speedo reading. Exact same thing happens if you just bought new tires and they're either larger or have more tread than they used to be.

Changing the speedo out will help, but that's because it's new. All old speedos loose track. Some people just get lucky.

 

[Effilcdar]

Serj is right to a point but that's talking about differences of a few mph. having a speedo that is around 20mph off is definitely not normal. I would Try and get a gauge assembly and vss out of a junkyard for comparison. It would really probably be easier (and definitely simpler) then testing things.

 

[Serj22]

Well, it is usually only a few MPH difference, but we've had CV's that are only 2 years old come up with doing 120 when doing 100MPH, and 30 actually doing 40mph. It depends. If it's way off, new gauge cluster or speedo.

Unless, you say it's in 5th doing 40 at 3500. Sometimes the speedo is actually physically broken and stops at certain points because of mechanical issues, not electrical. I'd just have it junkyard swapped.