Diagnose Engine Surges, Stalls, Misfires, Power Loss

Mass Air Flow Sensor failure symptoms

1. Low gas mileage, shuddering, stalling, knocking or pinging.
2. Check engine light may illuminate on the instrument panel.

Crankshaft Position Sensor failure symptoms

1. Engine may start normally in some cases, but will cut off after a few minutes (or seconds) of operation.
2. Engine may be unable to start at all.
3. No spark from the spark plugs.
4. Engine may experience backfiring or irregular rpm function, if the vehicle starts at all.
5. Long cranking time when starting cold
6. Engine may run rough on an intermittent basis, poor idle, poor acceleration, stumbling and/or hesitation.
7. Drop in mileage and stalling upon acceleration.

Camshaft Position Sensor failure symptoms

1. Engine may start normally in some cases, but will cut off after a few minutes (or seconds) of operation.
2. Engine may be unable to start at all.
3. No spark from the spark plugs.
4. Engine may experience backfiring or irregular rpm function, if the vehicle starts at all.
5. Long cranking time when starting cold
6. Engine may run rough on an intermittent basis, poor idle, poor acceleration, stumbling and/or hesitation.
7. Drop in mileage and stalling upon acceleration.

Throttle Position Sensor failure symptoms

1. A car that seems to hesitate or stumble during acceleration may have a faulty throttle position sensor.
2. If your car idles unevenly or hesitates intermittently, regardless of acceleration, the throttle position sensor may simply have a loose connection.

Oxygen Sensor failure symptoms

1. A sudden decrease in gas mileage.
2. Check engine light may illuminate.
3. Smog test failures can also be an indication of a failed oxygen sensor. EPA and CARB say 50 to 60% of all smog and emission tests related failures are attributed to the defective oxygen sensor. Faulty O2 sensor leads to either low or high CO emissions in the smog tests.
4. Engine may idle roughly, hesitate, or stumble. A bad oxygen sensor causes an engine's air/fuel mixture to become too lean. Normally, an air/fuel mixture that is too lean (too much air, not enough fuel) will cause an engine to miss, or misfire, especially when an engine is idling.

Knock Sensor failure symptoms

1. Check engine light may flash on your vehicle's dashboard.
2. If the knock sensor is not working properly, you will likely hear sounds emitting from the engine.
3. The vehicle will often shake or vibrate and misfire when the engine is started.
4. Stronger than normal exhaust and burning smells due to the detonation in the cylinders.
5. Fuel economy is often affected, causing the vehicle to burn more gas than usual and requiring frequent fuel replenishment.
6. May have acceleration problems, such as dragging, hesitation or jerking from the engine during speed increases.

Pick-Up Coil failure symptoms

1. A lack of spark because the spark plugs are not receiving the proper information to fire correctly.
2. The fuel injectors may fail to operate.
3. Rough idle may occur.
4. May cause engine stalling and an inability to accelerate smoothly.

Spark Plug Wires failure symptoms

1. Rough engine idle and/or misfire.
2. Engine hesitation, which is normally most apparent during acceleration.
3. Engine power loss and/or surging.

Ignition Switch failure symptoms

1. The dashboard lights will go off when the car stalls and the speedometer and tachometer (if you have one) will go off and come back on again.
2. Vehicle fails to start and stalls randomly while driving.
3. Switch gets overly hot.

Idle Air Control Valve failure symptoms

1. A faulty IAC will cause stalling problems at idle.
2. Most of the time if you hold the gas pedal down it will run fine. These symptoms can also come from an EGR valve that is stuck open.
3. If you have a fast idle, check for an intake leak.

Fuel Pump failure symptoms

1. Engine misfires causing the car to jump/buck occasionally while going along the highway. The fuel pump may act up for a mile or so two or three times and then run fine for the next 50 or more miles.
2. As you accelerate, the car starts to go and suddenly seems like it is going to die. Immediately, it seems to restart and off you go.
3. Power loss at highway speeds.
4. Will turn over, but will not start.

Timing Belt failure symptoms

1. No spark from the spark plugs.
2. Higher than normal amount of exhaust.
3. Difficult to start.
4. Engine may misfire, shake, hesitate, or stall if the timing is off.
5. Distributor rotor will not rotate.

Distributor/Cap/Rotor failure symptoms

1. Cylinder misfiring, engine shaking.
2. Trouble starting on a regular basis.
3. Starts okay but stalls and backfires once on the road.
4. High-pitched squealing noise.
5. A check engine light may be present.
6. If the distributor failed the vehicle will crank but not start.

Ignition Coil failure symptoms

1. A drop in power.
2. A total coil failure will cause a no spark, no run condition.
3. Decline in normal gas mileage.
4. May have black smoke out of the exhaust and smell of gasoline, rather than smelling like normal exhaust fumes.
5. May experience serious backfires, misfiring, and stalling.
6. Typically harder to start, especially when cold.

Ignition Control Module failure symptoms

1. High RPM misfire.
2. The car will start and run fine, but will stop running anywhere from seconds to minutes later. The engine may not restart immediately but if left to cool for about 10 minutes will start fine.
3. Hesitation/misfire under acceleration.
4. Failure to start.

Fuel Pressure Regulator failure symptoms

1. One or more of the spark plugs may have become fouled out and blackened.
2. When you are idling the engine it is not running smoothly and it is sputtering and spitting like it is going to die. If you haven't changed your fuel filter in a while, you should do that first and see if it helps. If not, then check the fuel pressure regulator.
3. Trouble starting the car. It will turn over but takes a few extra tries before it actually starts.
4. Tail pipe may have black smoke coming out of it.
5. Check the oil dipstick and see if you smell fuel on it.
6. Gasoline may be dripping out of the tailpipe.
7. The engine stalls when you press down on the gas pedal.

Fuel Filter failure symptoms

1. Engine may hesitate, stumble, or stall.
2. Rough engine idle.
3. Decrease in engine power.

Oil Pressure Switch failure symptoms

1. You might notice a leak from it, or a low oil pressure reading on the gauge.
2. The car will die out at times.

Vehicle Speed Sensor failure symptoms

1. The most common sign of a bad speed sensor is a speedometer or odometer that stops working. Also, you may not be able to set your vehicle to cruise control.
2. The following codes may be set: GM 24, Ford 27, 29, 452, Chrysler 28, 15
3. Typical OBD-II codes for a malfunctioning VSS are: P0500, P0501, P0502, P0503, P0716, P0718
4. May send out a wrong "too fast" signal, shutting down fuel flow at the wrong time.
5. Random or intermittent sudden loss of power and poor performance, only to have the engine resume normal operation.
6. Hesitation, roughness or sporadic jumps in your vehicle's transmission when you try to shift gears.
7. May rumble or idle irregularly when you start it, may burn more fuel than normal, may lose power suddenly due to wrong signals sent from the speed sensor to the fuel system.
8. Loss of anti-lock brakes, ABS warning lamps on the dash may be lit.
9. RPM limiter may be decreased.

Manifold Absolute Pressure Sensor failure symptoms

1. Engine will rev or surge suddenly, possibly causing the engine to sputter and die. May also surge while idling, such as at a stop light. You may also notice the engine idles rough when the car is on but not driving down the road.
2. The spark plugs may become fouled or coated with a white powdery substance.
3. Loss in engine power. Decreased fuel efficiency, consuming more gas than normal.
4. Check Engine Light may illuminate.
5. A rich or lean fuel mixture. May notice a gas smell even after warm-up and/or pinging at random times or all the time or whenever.
6. Rough idle and Hesitation.