The treadmill seems to surge or bog down when walking/running on and sometimes at speeds over 5mph the speedometer fluctuates from the speed it is set on.

A new treadmill is in order! It sounds like the motor is either old, or it has a factory default. Definitely do not use the treadmill if it produces burning smells this is in fact the wires in the motor heating up and melting this could cause a fire.

The speedometer can fluctuate rapidly under normal driving conditions when the car's speed changes abruptly, but sometimes the needle can start swinging around the dial without any fluctuation in speed. If the hairspring comes loose or breaks, it can't hold the speed cup in place, and the result is a fluctuation in the dial. In electrical speedometers, if the circuit that counts the magnetic pulses fails, it can cause the speedometer read-out to vary from the actual speed and to shoot upward or downward without notice. If a speed sensor in the automatic transmission starts to malfunction, it can affect the speedometer and cause fluctuations. In these instances, either the speedometer or the sensor needs replacement.

Precor Error E4, Incomplete Initialization Probable Cause Indicates that an incomplete upper PCA to lower PCA initialization occurred. When this error occurs, all lift motor and drive motor motion is ceased and the display will go blank except for the error displayed.
Corrective Action Run the initialization program. Caution: The treadmill's running belt will accelerate to the treadmill's maximum speed (12mph). DO NOT stand on the treadmill's running belt during the procedure.

1. Set the on/off switch to the OFF position. Wait a minimum of 10 seconds to allow the internal power supply to discharge.
2. Remove the safety key from the console and set the on/off switch to the ON position.
3. Press INCLINE UP and SPEED DOWN keys together. While pressing these keys, replace the safety switch on the console. Continue holding the INCLINE UP and SPEED DOWN keys until the display goes blank. INIT will appear in the time window of the display. The EEPROM is now clear and reset. After a second, 1.25 will appear in the distance/calories window, 15.0 (the maximum incline) will appear in the incline window, and 12.0 (the maximum speed) will flash in the speed/pace window.
4. Press QUICKSTART to begin the speed calibration process. Power bits will appear in the incline window, the target speed will appear in the time window and the actual speed will appear in the speed/pace window. At the beginning of the process, the target speed will be .5mph. The running belt will start. Once the actual speed reaches .5mph, the target speed will then change to 12mph and the running belt will accelerate until it reaches 12mph, then it will stop.
5. When the running belt stops, the display will return to the user mode and the initialization process is complete.

Precor Error Code E4

hi,
check the motor and the motor controlling card. check the motor is it over heating or not. also check the speed sensor beside the motor pulley. clean the speed sensor and refix it. then test again
ok

Walking Belt is Worn: The only certain way to test for a worn walking belt is to take a DC amp draw (if you have a DC treadmill) or an AC draw (for AC). Trying to look at the belt or a feel test is highly unreliable. Better tests, if you lack a DC ammeter (they are expensive for a good one), are a coast test or an incline test. The coast test is to get on the treadmill as the lowest incline setting and walk on the treadmill at 3 MPH. Pull the safety key and it should take you 2-3 full steps to stop (this is a general rule…some like a few Tunturi models stop on a dime even with a healthy belt but for most models, this tests works well upon). Fewer steps indicate high friction. The incline test is to put the treadmill at max incline and walk on it at 3 MPH. If the treadmill operates normally at max incline but bogs down at minimum incline, replace the walking belt. Gravity takes over for the drive system eliminating much of the friction problem. On some heavily worn walking belts, this test will not eliminate the problem. Go to your local hard ware store and purchase silicone spray. Apply Lubricant by lift one side of the running belt spray contents length wise starting at motor shroud to the back end repeat this process on the other side. If this unit bogs down again then you will have replace the running belt and possibly the deck

Use only a single-outlet surge suppressor that is
UL 1449 listed as a transient voltage surge suppressor
(TVSS). The surge suppressor must have a
UL suppressed voltage rating of 400 volts or less
and a minimum surge dissipation of 450 joules.
The surge suppressor must be electrically rated
for 120 volts AC and 15 amps. There must be a
monitoring light on the surge suppressor to indicate
whether it is functioning properly. Failure to
use a properly functioning surge suppressor could
result in damage to the control system of the
treadmill. If the control system is damaged, the
walking belt may change speed or stop unexpectedly,
which may result in a fall and serious injury.

Several issues, drive belt that drives the walking belt could be loose but you should smell rubber if its slipping.
Something could be caught in the track causing extra drag, its easy to do if you have kids or pets
Check for when you last lubed the track and walking surface, with no silicone it will drag and bog at low speeds

Its a loose connection on the speedo cable. its a b*tch to get to. I had the same problem on my truck, it would fluctuate in 5th gear on the highway. i spent the money and had a professional do it.

Precor Error E4, Incomplete Initialization Probable Cause Indicates that an incomplete upper PCA to lower PCA initialization occurred. When this error occurs, all lift motor and drive motor motion is ceased and the display will go blank except for the error displayed.
Corrective Action Run the initialization program. Caution: The treadmill's running belt will accelerate to the treadmill's maximum speed (12mph). DO NOT stand on the treadmill's running belt during the procedure.

1. Set the on/off switch to the OFF position. Wait a minimum of 10 seconds to allow the internal power supply to discharge.
2. Remove the safety key from the console and set the on/off switch to the ON position.
3. Press INCLINE UP and SPEED DOWN keys together. While pressing these keys, replace the safety switch on the console. Continue holding the INCLINE UP and SPEED DOWN keys until the display goes blank. INIT will appear in the time window of the display. The EEPROM is now clear and reset. After a second, 1.25 will appear in the distance/calories window, 15.0 (the maximum incline) will appear in the incline window, and 12.0 (the maximum speed) will flash in the speed/pace window.
4. Press QUICKSTART to begin the speed calibration process. Power bits will appear in the incline window, the target speed will appear in the time window and the actual speed will appear in the speed/pace window. At the beginning of the process, the target speed will be .5mph. The running belt will start. Once the actual speed reaches .5mph, the target speed will then change to 12mph and the running belt will accelerate until it reaches 12mph, then it will stop.
5. When the running belt stops, the display will return to the user mode and the initialization process is complete.

Precor Error Code E4