What is a limp mode

limp mode is a situation initiated by the ECM to protect the engine and/or the transmission
the problem is in the transmission and the TCM has lost continuity so at 2nd ratio it is shutting down the transmission so that more than 1 ratio cannot be selected together or the engine rpms can not go so high as to blow a motor
have the fault codes read to find the servo/ solenoid /sensor that has failed

The only thing these components have in common is the ground wires. There are many grounds on a vehicle. But the main three are the battery to body, battery to engine and engine to body. These are fairly large wires/cables. They should be checked with an ohm meter. I replace or repair any wires that have more than 5.0 ohms of resistance.

sensor failed or failing and ecu is in limp mode. you need to have the ecu read to find the fault as it can be one of many sensors cam/ crank, egr etc fault can trigger then the fault is gone but ecu will still be in limp mode. can take upto 30 starts to remove fault code and be out of limp mode.

Sounds like your vehicle is in limp mode. Check for faults with a fault code scanner at a local auto parts store. Resetting the fault will fix the limp mode, but not whatever caused your vehicle to initiate limp mode.

One of the accelerator position sensors may be bad putting it into limp home mode . Have it scanned for codes and post them here .

Check for fault codes for the idle speed sensor,accelerator position sensor and crank position sensor

When were the fuel filters changed.sounds like you have water in the fuel.Drain the tank and try new fuel after changing fuel filter.If it was in limp mode you would not get the revs droping down then smoke then picking up.Limp mode only alows you to do about 40mph.

It sounds like your transmission is going into the limp mode. The transmission goes into limp mode to protect the transmission from major damage. You either need to take it to the dealer or to a transmission shop to have a diagnostic test done.

sounds like a speedo converter gone if you have a *** import