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Published on January 8th, 2024
Innova R&D Team
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Innova diagnostic scanners assist you in understanding your vehicle, finding problems, and providing guidance for repairs. You can access the same advanced technology used by professionals, without the high costs or subscription fees.Learn more about Innova Scanners
Start all hands-on diagnostic routines with Hand and Eye Checks. In other words, look over the vehicle for obvious faults.
Note: All diagnostic routines should include the Hand and Eye Checks.
Noise, vibration and harshness (NVH) concerns have become more important as drivers have become more sensitive to these issues. Drivers have higher expectations of comfort levels. NVH issues are more noticeable due to reduced engine noise and better insulation in general. The main areas of the vehicle that produce NVH are:
It is necessary to isolate the NVH into its specific area(s) to allow more detailed diagnosis. A road test, as outlined later, is often the best method. The five most common sources of non-axle noise are exhaust, tires, roof racks, trim and moldings, and transmission. Ensure that none of the following conditions are the cause of the noise before proceeding with a driveline strip down and diagnosis.
Noise is very difficult to describe. However, the following are useful terms and are accompanied by suggestions as to when they are most likely to occur.
Check and rule out tires, exhaust and trim items before any disassembly to diagnose and correct gear noise.
The cause of noise can often be traced by first looking for leaks. A dry bearing or joint will produce significant noise.
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Clicking, popping or grinding noises may be noticeable at low speeds and be caused by the following:
The following may cause vibration at normal road speeds:
The following may cause shudder or vibration during acceleration:
Vibrations can be constant or variable. They can occur in every driving condition, or during a portion of the entire engine operating speed range. Vibrations are usually caused by some rotating component or components, or sometimes by the improper combustion of the air/fuel mixture in individual engine cylinders.
Under normal conditions, a rotating component will not produce a noticeable vibration. However, if the component is loose, misaligned, not properly balanced, or out-of-round, then a noticeable vibration can be produced. Engine vibrations that do not generate a noise are generally created by an out-of-round, out-of-balance or damaged component.
A vehicle will produce a certain amount of noise. Some noise is acceptable and may be audible at certain speeds or under various driving conditions such as on a new road. Carry out a thorough visual inspection of the vehicle before carrying out the road test. Keep in mind anything that is unusual. A key point is to not repair or adjust anything until the road test is carried out. Of course, this doesn't apply if the condition could be dangerous or the vehicle will not start. Establish a route that will be used for all diagnostic road tests. This allows you to get to know what is normal and what is not. The roads selected should have sections that are reasonably smooth, level and free of undulations as well as lesser quality sections needed to diagnose faults that only occur under particular conditions. A road that allows driving over a range of speeds is best. Gravel, dirt or bumpy roads are unsuitable because of the additional noise they produce.
If the concern is a noise or vibration on a particular road and only on a particular road, the source of the concern may be the road surface. Test the vehicle on the same type of road. Make a visual inspection as part of the preliminary diagnosis routine prior to the road test. Take note of anything that doesn't look right.
Road test the vehicle and define the condition by reproducing it several times during the road test. During the road test recreate the following conditions:
After a road test, it is often useful to do a similar test on a hoist or lift. When carrying out a ‘Shake and Vibration’ diagnosis or ‘Engine Accessory Vibration’ diagnosis on a lift, observe the following precautions:
Support the front suspension lower arm as far outboard as possible. This will ensure that the vehicle is at its correct ride height. The procedure is outlined by the following steps:
A test on the lift may produce different vibrations and noises than a road test because of the effect of the lift. It's not unusual to find a vibration on the lift that was not noticed during the road test. If the condition found on the road can be duplicated on the lift, carrying out experiments on the lift may save a great deal of time.
Sometimes, it helps to just push ahead and take a leap of faith! Learn more about our OBD2 scanners and how it can help diagnose the hidden issues with your vehicle.Get Started
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