Troubleshooting Engine Performance Problems

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:

1. Worn engine bearings: Replace crankshaft and connecting rod bearings. (Generally not a DIY job)

2. Broken engine parts: Replace broken engine parts.

3. Loose or missing flywheel mounting bolts: Replace and tighten loose or missing bolts. (Generally not a DIY job)

4. Loose or broken motor mounts: Replace motor mounts.

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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:

1. The PCV system is not working properly: Replace PCV valve.

2. The engine may have mechanical problems: Check compression to determine engine condition.

3. The engine's piston rings may be worn: Replace piston rings. (Generally not a DIY job)

4. The engine's valve seals may be worn: Replace valve seals. (Generally not a DIY job)

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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:

1. The engine's piston rings may be worn: Replace piston rings. (Generally not a DIY job)

2. The engine's valve seals may be worn: Replace valve seals. (Generally not a DIY job)

3. Damaged or worn valve guides: Replace valve guides. (Not a DIY job)

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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:

1. Transmission fluid may be entering the intake manifold through vacuum modulator: Replace vacuum modulator

2. Cylinder head gasket(s) may be bad: Replace cylinder head gasket(s).

3. Cylinder head(s) may be warped or cracked: Resurface or replace cylinder heads. (Resurfacing is not a DIY job)

4. The engine block may be cracked: Replace engine block.

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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:

1. If you have a carburetor, the carburetor choke may be stuck closed: Repair or replace choke.

2. Fuel injectors may be leaking: Replace fuel injectors.

3. You may have a dirty air filter: Replace the air filter.

4. There may be some other type of ignition problem: Check distributor cap and rotor. Ignition module may be bad

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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:

1. If the smoke has an oily smell, there is an oil leak: Repair oil leak.

2. If the smoke is white, there is probably a coolant leak: Repair coolant leak

3. If the smoke is blue or black and has a strong smell, there is wires burning: Repair wiring.

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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:

1. The PCV system is not working properly: Replace PCV valve. Check and repair PCV system as required.

2. The engine's gaskets and seals may be damaged: Replace gaskets and seals as required.

3. Oil filter may not be tightened properly: Tighten or replace oil filter.

_{Additional Information provided courtesy of ALLDATA DIY}

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