1. Transmission Problems: This is the MOST likely culprit. A speed limiter at 5mph strongly suggests a transmission problem. Possible issues include:
* Low Transmission Fluid: Check your transmission fluid level immediately. Low fluid can cause severe damage. The fluid should be red and not smell burnt.
* Transmission Failure: A failing transmission is a major problem that might require a rebuild or replacement. This could be due to worn clutches, a faulty valve body, or other internal damage.
* Transmission Shift Linkage: There's a mechanical linkage that connects the shifter to the transmission. A problem here could be preventing it from shifting correctly.
* Torque Converter Issues: A failing torque converter can prevent the car from accelerating properly.
2. Engine Problems: Though less likely to cause a 5mph speed limit, engine issues can also contribute:
* Spark Plugs and Wires: Worn or faulty spark plugs and wires can cause misfires, leading to poor acceleration.
* Fuel Delivery Problems: A clogged fuel filter, faulty fuel pump, or problems with the fuel injectors can restrict fuel flow, limiting speed.
* Throttle Body: A clogged or malfunctioning throttle body can restrict airflow to the engine.
* Mass Airflow Sensor (MAF) Sensor: A bad MAF sensor provides inaccurate readings to the engine control unit (ECU), leading to poor performance.
3. Brakes: While less likely to be the *only* problem, a problem with the brakes could be contributing.
* Emergency Brake: Make absolutely sure your emergency brake isn't partially engaged.
4. Other Potential Issues:
* Computer/ECU Problems: A faulty engine control unit (ECU) can cause a wide range of problems, including severely limited speed.
* Wheel Speed Sensors: Problems with these sensors can confuse the anti-lock brake system (ABS) and transmission control, leading to limp mode.
* Drive Shaft Issues: A broken or damaged drive shaft wouldn't allow power to reach the wheels.
What to Do:
1. Check Transmission Fluid: This is the absolute first thing to do. If it's low, add fluid of the correct type (consult your owner's manual). If it's low and dark or burnt smelling, you have a major problem.
2. Check the Emergency Brake: Make certain it's fully disengaged.
3. Have it Professionally Diagnosed: Given the severity of the issue (5mph maximum speed), taking it to a qualified mechanic is crucial. They have the tools and expertise to diagnose the underlying problem accurately. Avoid guessing and potentially causing more damage.
Trying to fix this yourself without experience could lead to more costly repairs down the line. A professional diagnosis will pinpoint the source of the problem and provide the best solution.
