I have noticed lately that my speedometer will bounce around wildly when the motor starts to see boost under hard aceleration. When driving normal, though, the speedo works just fine with no problems at all. The speed sensor is not too old either. Any ideas on what to check?
wheel spin lol na speed o cable is loose or wore out.
It's not wheel spin and there's no cable to be loose or worn out.
check your codes? I would guess the SDS is on its way out
95 spirit 3.0/543 15.0@91 N/A, 14.5@96 on a 50 shot RIP 87 shelby Z - project car, maybe I can drive it this year 91 spirit - roll it, chop the top, do some burnouts! RIP
Could be a loose connection. I've had the same thing happen to me, but it wasn't boost dependent.
Check/clean the connector at the SDS, next would be to follow the wires to the computer and check the connections there.
-Gary Mazzone-
1986 GLHS #168
Check your engine grounds. Add an extra one and see what happens.
I agree with the loose connection theory. It sounds to me like the engine is moving a little in it's mounts (normal) and the torque from going into boost is moving it enough to cause the loose connection to show itself. What connection to check is another story. Could be a ground, could be the SDS connector itself... I'd clean and tighten all the grounds, and clean the SDS plug to start with.
Forgive my ignorance here, but what and where exactly is the SDS plug? Thanks for the replies and I'll check the grounds in the mourning.
Nevermind on the SDS, it just hit me what it was.
speed distance sensor
Might be the connection Ill say. my lebaron use to do that too, ask matter of fact when i hit a bump it use to work for a while then die out. I found the wires to the pig tail falling apart check does while your looking at the SDS.
+1 on the poor connection. The speedo works in an ammeter function. Meaning it requires a certain amount of amperage through the magnet to decide what the needle will read. When the motor is loading up and rocking backwards, that could be causing you're short to become apparent at that moment. If it really bugs you that badly you could trace the circuit from the speedo to the speed distance sensor and check it's resistance, I would also loosen the front motor mount and rock the engine backwards to simulate the problem.
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