erratic speedometer

[george]

This morning my speedo in my 89 was reading very hi at slow speed. It buried the needle when I got up to crusing speed. the odo was going crazy also. After two miles at around 55 it went all the way down and then back to normal. It has never dun this before and there was no engine light. It is working normal now and I have not popped the hood to have a look.

YOu guys ever experienced this


car has 207k on it

[Oklahoma]

Is your car VSS or speedometer cable? I'm pretty sure 89 was the first year for the VSS. That would be the first thing I would look at, since if it was the speedometer head unit itself the odometer would not be doing weird stuff. Also, the fact that that was the first year for the VSS could mean that the system was more prone to failure-not yet perfected. My mom has a similar problem in her van (which uses a VSS) however it's the speedometer itself. The odometer and tachometer are fine. I replaced the VSS with a $5 JY unit to no avail... that said, I would put money on you needing a new VSS.

[a1veedubber]

Def the speed sensor. I had an old Corsica do this before, and it would actually cause the transmission to downshift into 1st gear at 80mph! Get it fixed asap!

edit: Strangely enough, the Corsica had a little over 200k when it went out too. It was located between the engine and the firewall, facing up.

[george]

I did open the hood and it LOOKs fine of course. I will have to special order one from autozone which is 63 plus shipping. Car did sit for two days which it usually gets driven everyday. funny I was just idling down the road and my speedo said 70mph. It pegged out right away at about 20mph and my odometer was adding mileage like crazy then I thought oh well no big deal this cars got plenty of miles already. Car did not drive or shift any differently than normal go figure. yeah it's a vss.

[george]

I will be picking up a new one at oreilly's saturday for 110.00 plus tax which would bring the total to 489 dollars jk.

uh if your car did what you say it did shifted into first at 80 that would suck. maybe you just saved my life. thanks

[george]

been readin the forums over at v6z24 and nobody states that the tranny could shift into first at a high rate of speed. I think that is almost impossible. but if the spedo drops the torque converter will unlock and I believe thats what happend to your corsica. also the plastic gear could be worn out so I will pull the vss tommorrow to see.

[george]

Plastic gear is fine and speedo was off again when drove to my other driveway into the garage. it read 50mph at maybe 10mph.

[SilentWing]

Yikes, at least the plastic gear is fine though, if you do replace the VSS and that fixes it let us know. The Only time my speedo ever acted up was when we had the engine out and we were testing different things without the body ground connected, but I'm sure a1 and oklahoma are right about the VSS.

[george]

It works thanks again

[george]

did it again this morning. it buried the needle then went to 10mph kept bouncing back and forth for about 4 miles and then works fine rest of the day. I think that one of the wires were it plugs into the vss is pinched. I'm going to straighten it out tommorrow and see if that helps. odometer was going crazy even when the needle was at 10 mph. car did not shift any differently.

[Prospeeder]

You car is too old dude, celebritys and 6000's didnt even GET electronic transmissions. Yours is completly mechanicly controlled with a TV cable and governor, possibly a vacuum modulator if its a 4 speed. The electronicly controled 4T60-E (thad be the 4 speed only, 3 speeds of any year stayed mechanical) came out in 1993 for the first year.

[george]

so your saying that my wacky speedo will never interfare with my 4spd tranny. does make sense.

[a1veedubber]

When it went out in the old 'Suck-a hatchback, it damn near blew the engine up. It started with what you are describing, but then got much worse. While driving on the interstate, the speedo suddenly went to about 10mph or so. I was actually going about 80-85 mph. The trans shifted into a VERY LOW gear (maybe second, I shifted into neutral almost instantly!). When this happened the tachometer instantly redlined and I broke every engine mount at once! So I know that it can cause "erratic" shifting in a 1990 Corsica Hatchback at least!!

When the computer went out in an old 2.5l 89 Eurosport I had as a beater once I swapped in one out of an 89 2.5l century. The car ran fine, but the speedo read about 50mph too fast and the odo raced like you are describing. I put the PROM from the old computer into the new one & the car was fine! There is a reason I like my old "Mechanical Everything" 86 Eurosport!!

[Prospeeder]

90 corsica with an electronic trans, hmmm

[george]

I fiddled with the wires this morning and then test it and it is still doing it. I tried straightning out the wire that has kinks in it and still whacky. But again after driving this morning about 2 miles it works fine the rest of the day. I think heat has something to do with it working. I think it's the wire is working when it gets warm. Unless there is something else that could be malfunctioning I'm going to cut the wire and have a closer look. cut some skin off that wire where it's got kinks and get rid of them.

[a1veedubber]

That would be awesome if it is just a loose wire......much cheaper than the sensor!!


edit: I like your wheels BTW!!!!

[george]

yeah although I already have a new sensor on it that was 120 bucks. I'm in illinois right now and will be going back to arkansas friday where I will start messin with the wire.

[george]

It was the computer(ecm).