Skip the auto shop - Our mechanics make house calls

Q: Load on truck's engine causes loud knocking noise

asked by on

When there is a load on my truck’s engine, there is a loud knocking noise. When I used a scanner, it registered a cylinder 5 misfire is detected. I have replaced the ignition coil, wires, and the plugs, but the problem still is existing. Can you tell me what is causing this knocking sound and give me advice on how to fix it?

A: Hello. It sounds like there may be a proble...

Hello. It sounds like there may be a problem with the piston or the valves in cylinder 5. Loose rod bearings to the piston can cause a knocking noise and/or a misfire condition. A worn out piston can also cause these symptoms. It is possible for a misfire to be caused by burnt valves but this will usually cause a tapping noise in the engine.

Since you have already replaced the ignition coil, wires, and spark plugs it is likely that there is an internal engine problem. In this case it may be necessary to have the engine rebuilt or replaced with a new one.

I suggest having the car looked at by a certified technician who can diagnose the noise in your engine firsthand and suggest an accurate repair from there.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Am I able to drive with misfiring cylinders?

Unfortunately, with two cylinders misfiring, this represents 50% of your motor not firing properly which results in a significant reduction of power output by your engine. While the car may be driven, this may be risky as this may cause...

Q: Truck stalls when stopping ocassionally. 2001 Mazda B4000

Hello. There could be a problem with the throttle position sensor or the idle air control valve. Both of these sensors help control proper air-fuel mixture and engine idle. Sometimes carbon builds up and clogs the idle air control valve...

Q: Warning lights come on after battery replacement

Hello. It sounds like the PCM (powertrain control module) and the BCM (body control module) have malfunctioned because of a shortage in the battery system. This could have happened when the battery failed, was removed, or installed. One explanation for...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.