I think it could be that the tires are too small, (or worn out). The smaller the tire, the faster it thinks the car is going. Or it could be that the traffic around you is actually going 120 as well... :grin:

 

Haha thanks, maybe its a bit of both.

But at 3000rpm in 5th gear it says I'm doing 135... and yet cars are passing me.

So it's unlikely to be a mechanical fault with the sensor in the gearbox etc?

 

I'm not sure how the speed sensor in the transmission is set up to work, so I couldn't say for certain how or what circumstances would lead it to send an exaggerated signal. One thing you can do though, is get someone to drive next to you at the same speed you are, and you could compare the speeds to see if your car is actually reading higher than it should. Another way to test is to have a gps that can tell you how fast you are moving.

 

My speedo used to read faster then I was actually going.
I stumble across a thread here that recommended pulling the speedo needle and adjusting accordingly.
When I changed my instrument cluster out for one with a tach I transfered my old speedo over and possibly put needle back on in wrong spot.
To get mine correct I had to actually move it under the little needle stop post then rotate it back up over the post to zero.
I checked my speed with one of those digital speed radars they occasionally mount on telephone poles.

 

Thanks, just trying to figure out if the speed is off proportionately or not. It seems to be changing so may not be the needle?

 

You can use an app on a smartphone to confirm your speed. If I recall correctly, mine read about 0-3 MPH faster than I was actually going.

 

Thanks, I did this. Sometimes it's off by 20km. Other times it's WAY off (phone says I'm doing 80 when spedo says 200km).

 

Is the amount it's off proportional to your speed (120 when going 100, 60 when going 50, 30 when going 25) or is it off a constant amount (120 when going 100, 70 when going 50, 45 when going 25)?

 

I'm not 100% sure but it seems to have changed and got worse. For example a few days ago it said I was doing 120 when I was doing 100. Now it is saying I'm doing over 200 when I'm doing 100.

Could it be the vehicle speed sensor?

 

I think the most likely explanation is related to Einstein's Special Theory of Relativity as it pertains to the speed of light.

 

Haha it would be the perfect time to do a Youtube video on how fast my Toyota Corolla 4AFE goes...

 

Is the odometer correctly marking actual miles? If it is then I'd guess the speed sensor is working correctly and the problem is in the speedometer mechanism or electronics. Sometimes a capacitor can go bad, but I'm not sure that would explain your symptoms, but I'm not sure it wouldn't either.

You can test the speed sensor output with an oscilloscope.

 

I just checked using an App on my phone & the distance travelled is correct. It's just the speed which is way off.

 

Some related:

http://www.toyotanation.com/forum/1...a-7th-generation-1993-1997/1383257-1993-corolla-speedometer-all-over-place.html
http://www.toyotanation.com/forum/1...forum/130-corolla-7th-generation-1993-1997/1402657-speedometer-malfunction.html
http://www.toyotanation.com/forum/1...lla-7th-generation-1993-1997/930521-need-help-adding-tach-93-a.html#post9755994

 

I had a similar problem with my '93 Geo Prizm (a Corolla clone) back in '09. Only difference was that the spedo was showing 55 when I was actually doing 70. I suspect the same fault, however. Chances are you need a new speedometer 'head,' which is the dial in the center of your instrument cluster. That part isn't sold new though and you're probably going to have to find a complete cluster (used ones should be good.) The spedo heads are interchangeable, but you're going to get a different odometer with a different mileage reading in the process.