Wakko speedo

1992 olds 88 3.8. Car runs great, no cruise (suprise) and now for the big whammy.....When moving about 20mph the speedo shows 90mph...Is this caused by the speed sensor?

I had the same problem with my 92' 88. It turned out to be the computer box that is located under the glove compartment. I bought one at the junk yard for $50 bucks any put it in. Solved my problem.

Man that's just messed up. I thought I had the fastest Olds in history...lol....0-120 and back to 0 in 3.8 seconds. It didn't make sense because the odometer was accurate...What is the computer called and what does it do?runaround

the computer is called the ecm (electronic control module) and it does just that.

in other words it takes all of the information from all of the different sensor located throughout the car and uses them to keep the engine runing with the best ratio of air to fuel, power and economy and tells you if something is wrong with the engine. In the occurance of a faulty sensor the ecm will still keep the engine running with a the factory default ratios, or in the case of the little black square mounted in you key, prevent it from running.