This may be covered somewhere but I couldn't find it. After a couple of months on not driving my 89 RS I cranked up to go for a drive recently and noticed that even though the engine was not over revving my tach was indicating about 3000 rpm and when up to road speed it increased to around 7000. After a short drive and time to warm up when I stopped for a stop sign it came down to a reasonable 900 or thereabouts but went back up to the peg when up to road speed. I am certain based on sound and such that the engine was not turning anywhere near that fast. Trans shift appeared normal etc. The car has a 305 which as far as I know is original. I bought it some years ago with less than 100,000 on the clock but currently have about 247,000 on it. Any ideas what is wrong and how to fix???

 

speedometer cable could have went out after all of those miles. I own a 89 Rs too, the speedo was busted took about 1/12 hour to replace.

 

Thanks for the reply. The speedo seems to be working fine except for the trip odometer which stuck sometime back when I zeroed it. Is it possible that the two are tied to the same cable and one work and the other not?

 

Something's screwy between the ignition coil and the tach... Speedo is completely independent of the tach, so even if the cable to the speedo were bad, the tach would do the same. Check the resistance on the white wire at the coil between the coil and the dash pin.

 

Thanks, appreciate the tip. Since it sat without cranking for a couple of months and I live near the beach corrosion seemed the most likely problem but I didn't know where to start.