First, did you change your original equipment tire size? If not, many shops have dynomometers that can calculate how far off your speedometer is, if it is way off there are a few things that you can do to fix it which one these shops can give you the full details on
Most likely speedometer cable
You would fix it by replacing the instrument cluster. The speedometer itself may not be faulty, it is more likely to be a problem with the speed sensor.
You can fix the speedometer in your 1994 Oldsmobile 98 by replacing the speedometer cable. If changing the speedometer cable does not fix your speedometer you will need to replace the entire speedometer.
we had to replace the speed sensor in mine and it corrected the problem with the speedometer and the shifting. Good luck
I had that problem in my 84 and it turned out to be the cable itself
It seems as if there is a problem with the wiring between your speedometer and AC/heat unit. A licensed repairman can determine and fix the cause of this problem.
A speedometer that loses response time but gets up to the speed of the vehicle probably has a problem with a gear slipping inside the speedometer mechanism. This sometimes happens in older vehicles. The speedometer cable may have to be replaced to fix this problem.
Most common would be speedometer cable has broken Remove speedometer head and move vehicle to see if cable moves- if not probably broken - if it does probably problem with speedometer head
I had same problem on mine , the exhaust milted the rubber right into the cable on drivers side. you need a new one
Speedometer is ran by electronic sensor on rear end. Odometer is ran from speedometer. If both don't work problem is sensor. If speedometer works sensor is okay. If speedometer works and odometer does not problem is in mechanical parts (gears) of of odometer and has to be replaced. Can get used from eBay (search for speedometer or odometer, is one unit) or take to dealer.
how to fix speedometer for Toyota mr2
Its probably the vehicle speed sensor located on the transmission. Mine had that problem