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speedo woes and overdirve uncertainty


cb84capri

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hello i'm new to the site. i have a 92 lumina euro, 3.1. was wondering if any of you guys have seen this problem before or know what it is.

 

seems like when i travel over 50mph the speedo starts to go all over the place. if i try to hold any speed above that it kicks in an out of overdirve. it it very frustrating to drive. it just started doing this to me a few days ago and i'm trying to avoid driving it right now.

 

just before this started, i noticed my cruise control was surging a lot. so i stopped using cruise. it would really test my stomach if i did. and none of this has turned on the check engine light.

 

the tranny fluid was clean and in range on the dipstick when i checked a month ago. it shifts through the other gears fine and speedo reads fine until over 50mph. if i travel over 50mph for a long time then the the speedo is messed at any speed below 50mph. it reads 0 ok however.

 

any idea what to do? i've tried to describe this as best i can. is this an electronically shifted transaxle, or electronic overdrive? i'm kind of leaning towards the vehicle speed sensor myself - if it even has one. vehicle speed isn't read off a wheel speed sensor on this car is it?

 

thanks in advance,

cale

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being a 92 and a 3.2 it should not have an electronic transmission.

 

HOWEVER, it will have a lockup torque converter, which may be turned on and off in response to the fluctuation speed readings, this may be what you are experiencing.

 

a new WTFBBQSAUCE do you call it??? the speedo signal is generated by a sensor on the transmission, that part could be bad, but you could also have damaged wires leading to and from that sensor.

 

 

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new WTFBBQSAUCE do you call it???

 

Ken's learning :lol:

 

Sounds odd, it only happens around that speed? Are you sure it's not a misfire?

 

I would say one of three things, in particular:

 

Bad speedo sensor, as Ken suggested (located on passenger end of transaxle, near the axle, I think it faces the passenger side wheel well).

 

Bad coilpacks (I would start by checking spark plug condition/gap first) - known symptom with 3.1/4T60s, under load at highway speed (just into 4th), the motor misfires because a coil pack is going bad and isn't putting out enough juice to handle the power load.

 

Failing fuel pump or clogged fuel filter, or maybe a bad injector.

 

 

It could be the torque converter or the lockup solenoid, I would expect one of the above first. Definitely due tune-up items first (plugs and fuel filter), then eliminate possibilities from there. That said, however, the fact that you said the speedo is screwed up at lower speeds after that leads me to believe it may just be the speed sensor. Does it drive funny at the lower speeds? or is just the speedo acting funny?

 

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