Weird speedometer readings

[ChitownDSM]

I am not sure if this has come up before because I did mutiple searches and couldn't find anything. Well here is the issue. When I start my car the speedometer just randomly goes up to like between 40-80mph. Now once the car warms up it rests back down at the needle approx 2-3 minutes after start. Now once I start driving the speedometer shows around 10 times the actuall speed I am going. 5mph shows 50mph. Once the car is driven for like 30-minutes to over an hour at time it will finally even back out and start showing a correct reading. I haven't changed anything in the car recently besides putting in a SAFC II but I didn't mess with any non needed wires. I am really needing to figure out what is going on with this speedometer so any help would be very much appriciated. Thanks

 

[turbodsm18]

First question to ask yourself, Did it do this before you put your SAFC on the car

 

[ChitownDSM]

No but the car sits for long periods of time. We haev put on a bunch of bolts on in the engine bay but electrically this is the only mod we have made.

 

[Dream On]

I'd recheck the wiring for the SAFC.

 

[turbodsm18]

I'd recheck the wiring for the SAFC.

X2

If it didnt do this before the SAFC then that has got to be it.

 

[Defiant]

And check the security of the speedo sensor's plug on the gearbox.