Diagnose Engine Surges, Stalls, Misfires, Power Loss

Camshaft 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.

Crank 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.

Distributor failure symptoms

1. Cylinder misfiring, engine shaking.
2. A check engine light may be present.
3. If the distributor failed the vehicle will crank but not start.

Distributor Cap 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.

Fuel Filter failure symptoms

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

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 Pump failure symptoms

1. Engine misfires causing the car to jerk 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.

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.

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.

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 is fails to start and stalls randomly while driving.
3. Switch gets overly hot.

Knock Sensor failure symptoms

1. Often a bad knock sensor will trigger the “check engine” light to 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. The engine may emit strong 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.

Mass Air Flow Sensor failure symptoms

1. MAF failure can cause a range of engine performance problems including low gas mileage, shuddering, stalling, knocking or pinging.
2. The most reliable early symptom of a failing or failed MAF is the illumination of the check engine light on the instrument panel.

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.

Oxygen Sensor failure symptoms

1. A sudden decrease in gas mileage
2. The defective oxygen sensor can also show up as a check engine light or malfunction indicator lamp illuminating in the vehicle’s dash board.
3. Smog test failures can also be an indication of a failed oxygen sensor. EPA (Environmental Protection Agency) and CARB (California Air Resource Board) 50 to 60% of all smog test / emission test 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. A bad oxygen sensor can cause a car’s engine to idle roughly. 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.
5. A bad oxygen sensor may misread or misinterpret an engine’s air/fuel mixture as being lean, especially during acceleration. This can cause an engine to hesitate, or stumble.

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.

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.

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.
6. Camshafts will not rotate.

NOTE: Some symptoms may vary from vehicle to vehicle due to varying device designs, but generally these symptoms apply. This is meant as a guide, so before you go out and buy new replacement parts, unless you have the money to spare, take time to diagnose and check the parts in question.