Resolved 91 LX 5.0 Rpm Gauge on the stock Cluster problem...

[Mindseye007]

sometimes when I start my car and start driving all of a sudden the rpm gauge will go up to redline and stay there, it's like how the new cars are when you start them up so after about 5 minutes of driving the rpm goes back to normal? why is this?

I Solved this problem as it was my TFI module burning out, changed the TFI and the rpm gauge was back to normal operation again.

 

[Mustang5L5]

Do you have anything connected to the coil wires? Aftermarket tach ignition.

That's not normal behavior, but the tach works of a frequency signal. It's either getting the signal from something that is connected to the tach wiring, or defective itself.

 

[Mindseye007]

Do you have anything connected to the coil wires? Aftermarket tach ignition.

That's not normal behavior, but the tach works of a frequency signal. It's either getting the signal from something that is connected to the tach wiring, or defective itself.

I have a small shift light .

 

[Mindseye007]

Do you have anything connected to the coil wires? Aftermarket tach ignition.

That's not normal behavior, but the tach works of a frequency signal. It's either getting the signal from something that is connected to the tach wiring, or defective itself.

I have a small shift light .

Autometer

 

[Mustang5L5]

When you power the car up, does the shift light display the light for a second?

Does it match the tach sweep?

 

[Mindseye007]

When you power the car up, does the shift light display the light for a second?

Does it match the tach sweep.

Yes it does display the light for a second . The cluster rpm gauge acts normal to,
its while the motor is running all of a sudden it jumps up into redline then after a few minutes of driving it goes back to normal so weird .

 

[Mustang5L5]

Can you temporarily disconnect the shift light and see if the issue disappears?

If the tach jumps and the motor isn’t misfiring, my initial thought it interference from another device. A wayward signal from the shift light for instance

 

[Mindseye007]

M

Yes it does display the light for a second . The cluster rpm gauge acts normal to,
its while the motor is running all of a sudden it jumps up into redline then after a few minutes of driving it goes back to normal so weird .

My fuel gauge gauge goes way up past f mark too so I bought a brand new slosh module I had the grounds checked everything is ok by the fuel tank going to install it soon you think that might fix the cluster rpm gauge problem as well?

 

[Mindseye007]

So weird I had that shifter installed a few years ago by dasilva racing never had a problem till last summer .

 

[Mindseye007]

Can you temporarily disconnect the shift light and see if the issue disappears?

If the tach jumps and the motor isn’t misfiring, my initial thought it interference from another device. A wayward signal from the shift light for instance

What else might cause interference and thanks so much for you help with my problem.

 

[Mustang5L5]

Unknown if it will fix it. Part of the trial and error process.

The tach and fuel Guage share the same 12v power but the grounds are different. Unknown if those two issues are related

 

[Mindseye007]

Unknown if it will fix it. Part of the trial and error process.

The tach and fuel Guage share the same 12v power but the grounds are different. Unknown if those two issues are related

I just installed a brand new slosh module and I noticed the power wire and negative wire for the shift light were wrapped around the speaker wire would that have any effect

 

[Mustang5L5]

I just installed a brand new slosh module and I noticed the power wire and negative wire for the shift light were wrapped around the speaker wire would that have any effect

Unknown, but it certainly wouldn't help the situation as that could be a source of interference. I would correct it regardless and separate the wires.