Ron's Pit Stop

Troubleshooting Engine Performance Problems

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There are many things that can effect engine performance. Today’s cars are more complicated then they ever were. Electronic components and computers make them more fuel efficient, but they also make them more complicated and difficult to troubleshoot.
A lot of things that made an engine run bad twenty years ago, still hold true today. The electronics make
the engine run, but under all those electronics the engine has basically remained the same. Before you try
and troubleshoot any problem, you need to check the basics. The engine needs spark, fuel and air to
operate and nine times out of ten, it's a simple and basic problem.
Please note that some of these test may not be applicable to your vehicle and some of the sensors may no longer be used on your vehicle.

Engine hesitates:

When you step on the gas, the engine seems to bog down or takes a second to respond. You may notice a general lack of power. You may notice the problem when the engine is hot or cold or when you are low on fuel.

Possible causes:

  • You may have a dirty air filter: Replace the air filter.
  • The spark plugs may be dirty or worn: Clean and regap spark plugs. Replace spark plugs.
  • The ignition wires may be bad: Replace ignition wires.
  • There may be some other type of ignition problem: Check distributor cap or rotor. Ignition module may be bad.
  • You may have water in the gasoline: Drain the gas tank and flushed with fresh gas and refill. (Generally not a DIY job)
  • If you have a carburetor, you may have a bad accelerator pump or power circuit: Replace accelerator pump or replace carburetor.
  • The fuel filter may be clogged: Replace fuel filter.
  • Your catalytic converter may be clogged: Replace catalytic converter.

    The engine surges or misfires while moving:

    The engine seems to start fine and will normally accelerate fine. As you are driving and maintaining a steady speed, the engine seems to "speed up" slightly or it seems to miss and buck.

    Possible causes:

  • If you have a carburetor, the choke may not be set properly, or the choke may not be working correctly: Check the choke plate and make sure it is opening completely.
  • The engine may be running too hot: Check and repair cooling system.
  • The fuel pressure regulator may be operating at too low of a pressure: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)
  • The ignition timing may be set wrong: Adjust ignition timing.
  • There may be some type of ignition problem: Check and replace distributor cap, rotor, ignition wires and spark plugs.
  • There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
  • The fuel filter may be partially clogged: Replace the fuel filter.
  • The torque converter in the transmission may not be locking at the right time, or it may be slipping: Check lock up circuit or replace torque converter. (Not a DIY job)
  • There may be a vacuum leak: Check and replace vacuum lines as required.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • The EGR valve may be stuck open: Replace EGR valve.
  • The drive axles may be loose or worn: Check and replace CV/universal joints as required.
  • The fuel injectors may be dirty: Clean or replace fuel injectors.

    A hissing sound is heard from the engine:

    The engine may or may not seem to run well. A hissing noise like air or steam can be heard coming from the engine. A performance drop may be noticed immediately after the noise begins.

    Possible causes:

  • The engine is overheating: Check and repair cooling system.
  • The exhaust system and/or catalytic converter are plugged: Check and replace exhaust system and/or catalytic converter as required.
  • A vacuum line is leaking or disconnected: Reconnect vacuum line. Replace vacuum lines.
  • A vacuum device is leaking: Replace vacuum device.

    Whirring from the engine that gets worse as engine speed increases or decreases:


    Possible causes :

  • Low power steering fluid: Check and fill power steering fluid.
  • The alternator bearings are bad: Replace alternator.
  • A bad water pump: Replace water pump.
  • A bad power steering pump: Replace power steering pump.
  • A bad air conditioning compressor: Replace air conditioning compressor. (Not a DIY job)

    Loud exhaust:

  • There is a loud exhaust noise which may be coming from either the front or rear of the vehicle.

    Possible causes:

  • Muffler or exhaust pipe worn out: Replace muffler and/or pipes as required.
  • Exhaust manifold cracked or broken: Replace exhaust manifold.

    Engine backfires when you press on the gas pedal:

    The engine runs like garbage. When you step on the gas the engine pops, spits and backfires. Sometimes it's loud or not so loud. This can cause severe engine damage and/or under hood fire.

    Possible causes :

  • Your camshaft timing belt or chain may have slipped: Replace timing belt or chain.
  • Your ignition timing needs adjusting: Adjust ignition timing.
  • There is a serious engine problem: You may have a burnt or broken valve, Worn or broken camshaft.
  • Your spark plug wires are placed on the wrong spark plugs: Check firing order and place the wires on the correct spark plugs.

    Engine hesitates, and a popping is heard from the engine:

    When you step on the gas, the engine seems to bog down or takes a second to respond. You may notice a general lack of power. You may notice the problem when the engine is hot or cold or when you are low on fuel. The popping noise really tells you something is not right.

    Possible causes:

  • You may have a dirty air filter: Replace the air filter.
  • The ignition wires may be bad: Replace ignition wires.
  • There may be some other type of ignition problem: Check distributor cap or rotor. Ignition module may be bad.
  • The engine may have mechanical problems: Check compression to determine engine condition

    Engine makes a tapping noise when idling:

    As the engine is idling, you hear a tapping noise coming from the engine. You don't notice the tap when you are moving or when you increase the speed of the engine. The problem seems to get worse (noisier) when the engine is warm. The tapping is also getting more noticeable every day.

    Possible causes:

  • Your valves need adjusting: Check and adjust valves.
  • The engine is low on oil: Check oil level and fill as required.
  • The engine's oil pressure is low: Check oil pressure. Replace oil pump. (Generally not a DIY job)
  • Hydraulic valve lifters bad: Replace valve lifters.
  • Push rods bent or worn out: Replace push rods.

    Popping noise from exhaust:

    Whenever you press on the gas, you hear a popping from the exhaust. It may or may not be very loud and the engine seems to run okay. You may notice a drop in gas mileage.

    Possible causes:

  • Muffler or exhaust pipe worn out: Replace muffler and/or pipes as required.
  • Exhaust manifold cracked or broken: Replace exhaust manifold.

    Engine makes a ticking noise:

    As soon as you start the engine, you hear a ticking noise. It sounds like a pencil tapping. The speed of the noise increases with an increase in engine speed.

    Possible causes:

  • The valves need to be adjusted: Adjust valves.
  • There is sludge in the engine which is restricting oil flow: Flush engine, replace oil filter and fill with new oil.
  • Hydraulic valve lifters bad: Replace valve lifters.
  • One or more of the engine's valves are stuck: Check valves and repair. (Generally not a DIY job)
  • Push rods bent or worn out: Replace push rods.

    There is a rattling noise from the engine when you accelerate:

    Your car runs well all the time. But when you press on the gas pedal to accelerate or to go up a hill, the engine rattles like the cylinders are full of marbles.

    Possible causes:

  • The ignition timing may be set wrong: Adjust ignition timing.
  • The engine may be running too hot: Check and repair cooling system.
  • There may be a vacuum leak: Check and replace vacuum lines as required.
  • Incorrect grade of fuel: Fill with the correct, or higher, octane fuel.
  • There is an excessive amount of carbon built up in your engine: Clean carbon from valves and combustion chamber. (Not a DIY job)
  • There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)

    Squealing from engine while accelerating:

    An irritating squeal is heard as you accelerate, turn a corner, or slow down. You may also notice that the noise is more frequent when the air conditioning is turned on.

    Possible causes:

  • The drive belts are slipping: Replace belts.
  • The drive pulleys for some engine accessories are misaligned: Repair or replace bent pulleys. Check belt routings.
  • You have turned the steering wheel to the limits: Normal.
  • The drive belts are loose: Tighten belts.

    Clunking from the engine that worsens when engine speed increases:

    When you step on the gas pedal, the engine makes a clunking noise. The noise gets worse as you press harder on the gas pedal. The noise is present in gear or in neutral. Sometimes the noise is not noticeable when you are letting the engine idle but occurs as soon as you step on the gas.

    Possible causes:

  • Worn engine bearings: Replace crankshaft and connecting rod bearings. (Generally not a DIY job)
  • Broken engine parts: Replace broken engine parts.
  • Loose or missing flywheel mounting bolts: Replace and tighten loose or missing bolts. (Generally not a DIY job)
  • Loose or broken motor mounts: Replace motor mounts.

    Engine uses more oil than normal, and there is some smoke from the exhaust:

    The oil level is low between oil changes. It appears that the oil is being burned by the engine because of the smoke in the exhaust. You may or may not notice the engine doesn't have the same power as it used to.

    Possible causes:

  • The PCV system is not working properly: Replace PCV valve.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • The engine's piston rings may be worn: Replace piston rings. (Generally not a DIY job)
  • The engine's valve seals may be worn: Replace valve seals. (Generally not a DIY job)

    Gray smoke from the exhaust:

    You notice gray smoke coming from the exhaust when you start your car. The smoke may or may not disappear after the car is warmed. If it is, it is less noticeable. The smoke may have a bluish tint to it.

    Possible causes:

  • The engine's piston rings may be worn: Replace piston rings. (Generally not a DIY job)
  • The engine's valve seals may be worn: Replace valve seals. (Generally not a DIY job)
  • Damaged or worn valve guides: Replace valve guides. (Not a DIY job)

    White smoke or water vapor from the exhaust:

    You notice white smoke coming from the exhaust when you start your car. If it is cold out, this may be normal. If the smoke does not disappear after the car is warmed, you have a problem.

    Possible causes:

  • Transmission fluid may be entering the intake manifold through vacuum modulator: Replace vacuum modulator
  • Cylinder head gasket(s) may be bad: Replace cylinder head gasket(s).
  • Cylinder head(s) may be warped or cracked: Resurface or replace cylinder heads. (Resurfacing is not a DIY job)
  • The engine block may be cracked: Replace engine block.

    Black smoke from the exhaust:

    You notice black smoke coming from the exhaust when you start your car. The smoke may or may not disappear after the car is warmed. If it is, it is less noticeable. Engine may or may not be running rough or misfiring.

    Possible causes:

  • If you have a carburetor, the carburetor choke may be stuck closed: Repair or replace choke.
  • Fuel injectors may be leaking: Replace fuel injectors.
  • You may have a dirty air filter: Replace the air filter.
  • There may be some other type of ignition problem: Check distributor cap and rotor. Ignition module may be bad

    Smoke is coming from under the hood:

    Mainly you will only see the smoke when you start your car or when you stop at a traffic light or stop sign. The smoke may or may not be accompanied by engine idling problems. This should not be ignored as it may lead to engine damage or fire. The cause of the problem is best identified by the color, smell, and amount of smoke.

    Possible causes:

  • If the smoke has an oily smell, there is an oil leak: Repair oil leak.
  • If the smoke is white, there is probably a coolant leak: Repair coolant leak
  • If the smoke is blue or black and has a strong smell, there is wires burning: Repair wiring.

    Engine is using more oil than normal. Oil puddles under the car when parked:

    The oil level is low between oil changes. You see puddles of oil under the car. Obviously you have an oil leaks. You may or may not see smoke or smell oil burning when you stop at a light, stop sign. or park the car. You should make sure the engine always has the proper oil level.

    Possible causes:

  • The PCV system is not working properly: Replace PCV valve. Check and repair PCV system as required.
  • The engine's gaskets and seals may be damaged: Replace gaskets and seals as required.
  • Oil filter may not be tightened properly: Tighten or replace oil filter.

    Engine quickly overheats:

    Engine runs fine but gets very hot shortly after you start it. This problem usually occurs after only five minutes of running or after traveling about a mile. You may or may not notice steam coming from the hood or smell coolant.

    Possible causes:

  • Engine coolant level may be very low: Refill coolant to proper level.
  • Engine's drive belts may be broken or slipping: Tighten or replace belts.
  • The electric cooling fan may not be coming on: Repair or replace cooling fan. Repair wiring. Replace cooling fan temp sensor.
  • The ignition timing may be set wrong: Adjust ignition timing.
  • There may be a vacuum leak: Check and replace vacuum lines as required.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • The engine's thermostat may be stuck closed: Replace thermostat.
  • There may be a leak in the cooling system: Repair leak and refill coolant.
  • Cylinder head gasket(s) may be bad: Replace cylinder head gasket(s).

    Engine overheats:

    Engine runs fine but gets very hot while driving. This problem usually occurs after moderate to extended periods of driving. You may or may not notice steam coming from the hood or smell coolant.

    Possible causes:

  • Engine coolant level may be too low: Refill coolant to proper level.
  • Engine's drive belts may be broken or slipping: Tighten or replace belts.
  • The electric cooling fan may not be coming on: Repair or replace cooling fan. Repair wiring. Replace cooling fan temp sensor.
  • The ignition timing may be set wrong: Adjust ignition timing.
  • There may be a vacuum leak: Check and replace vacuum lines as required.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • There may be a leak in the cooling system: Repair leak and refill coolant.
  • Cylinder head gasket(s) may be bad: Replace cylinder head gasket(s).
  • Car is over loaded or driven too hard: Lighten the load and back off the gas.
  • The radiator or block may be clogged: Reverse flush cooling system and fill with fresh coolant.

    Your engine or oil light comes on while driving:

    The oil light may be marked engine. If this is the case, this light and warning system monitors the water temperature of the engine in addition to the oil. If this light stays on regardless of how fast you run the engine, there is a serious problem. Sometimes the light will come on when the engine is idling and go out when the engine's speed is increased. In most cases, this problem becomes more evident as the problem gets worse.

    Possible causes:

  • The engine has lost oil pressure or has low oil pressure: Oil pump has failed. Stop the engine and have it repaired. (Not a DIY job)
  • The oil pressure sending unit is bad: Replace sending unit.
  • The engine is very low on oil: Check and fill oil.
  • The engine is overheating: Repair cooling system.

    Your check engine or service engine light comes on or stays on:

    This can be a very confusing situation since all manufacturers have called this light by different names. Additional confusion is caused since manufacturers have different systems that are monitored by this light. In most cases, this light is part of the electronic engine control system. When the light comes on, it means that the car's computer has detected something wrong in the control system. The lamp remains lit until the problem is corrected. In some systems, it could just indicate that there is a problem. The warning light may suddenly come on and remain on, or it may come on and go out after a period of time.

    Possible causes:

  • The engine's computer has detected a problem in the system: Have system checked with a scan tool to determine problem. (Generally not a DIY job)
  • The engine's oil pressure is extremely low: Stop engine and do not resume operation until cause of low oil pressure has been determined and repaired.
  • The engine is overheating: Repair cooling system.

    The car uses more fuel than normal, and there is a strong odor from the exhaust:

    You notice that gas mileage has gone down quite a bit. There is a strong smell like rotten eggs coming from the exhaust. You may or may not have noticed that the car doesn't have the same amount of power it used to.

    Possible causes:

  • If you have a carburetor, the carburetor choke may be stuck closed: Repair or replace choke.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • The ignition timing may be set wrong: Adjust ignition timing.
  • There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
  • The engine may be running too hot: Check and repair cooling system.
  • The fuel injectors may be stuck partially open: Replace injectors.
  • There may be an emission-control device that is not working properly.
  • There may be some type of ignition problem: Check and replace distributor cap, rotor, ignition wires and spark plugs.
  • The fuel pressure regulator may be operating at too high of a pressure: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)

    Engine seems to use more fuel than normal, and there is a strong gas odor coming from the car:

    You notice that gas mileage has gone down quite a bit. There is a strong smell of raw fuel coming from the engine when you shut it off. You may or may not have noticed that the car doesn't have the same amount of power it used to.>

    Possible causes:

  • The fuel lines may have a leak: Replace or repair fuel lines.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • The fuel pressure regulator may be operating at too high of a pressure: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)
  • The fuel injectors may be leaking: Replace injectors.
  • Gas cap may be missing or bad: replace gas cap.

    There is a rotten egg smell coming from the exhaust:

    Whenever you run the engine and are standing still, you notice an awful smell from the exhaust. The smell is like that of rotten eggs.

    Possible causes:

  • There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
  • There may be some type of ignition problem: Check and replace distributor cap, rotor, ignition wires and spark plugs.
  • The fuel pressure regulator may be bad: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • The engine may be running too hot: Check and repair cooling system.

    There is a strong gas smell coming from the exhaust:

    You notice the smell of raw gas from the exhaust. You think you have a gas leak. Not only do you notice the smell, so does everyone around your car. You may or may not have noticed a drop in your gas mileage.

    Possible causes:

  • There may be a fault in the computerized engine control system: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
  • There may be some type of ignition problem: Check and replace distributor cap, rotor, ignition wires and spark plugs.
  • The fuel injectors may be dirty: Clean or replace injectors.
  • The engine may have mechanical problems: Check compression to determine engine condition.
  • If you have a carburetor, the carburetor choke may be stuck closed: Repair or replace choke.
  • You have a vacuum leak: Repair or replace vacuum lines.

    Engine doesn't want to increase its speed:

    When you step on the gas, the engine seems to slow down and sometimes it stalls. You have to press down on the gas pedal very slowly to increase the speed of the engine. Even with that, the car doesn't seem to move like it should, and there is a general lack of power. You may or may not notice the problem when the engine is hot or cold.

    Possible causes:

  • You may have a dirty air filter: Replace the air filter.
  • The fuel filter may be clogged: Replace fuel filter.
  • The ignition timing may be set wrong: Adjust ignition timing.
  • You may have water in the gasoline: Drain the gas tank and flushed with fresh gas and refill. (Generally not a DIY job)
  • Your catalytic converter may be clogged: Replace catalytic converter.
  • The fuel pump may be bad: Replace fuel pump.