Noise above 40 mph

ANSWER : This may be a sign of a dirty or failing mass air flow sensor. The mass air flow sensor is a unit in the intake system that monitors air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This may cause a hesitation, loss of power or jerking reaction when this sensor is malfunctioning. When this is not working properly, you may also notice a strong smell of fuel. I would suggest having a professional from Your Mechanic come to your home to diagnose your mass air flow sensor.

ANSWER : It’s great that you are trying to be your own detective! This information is very helpful for a mechanic who isn’t there to hear the noise. My first thought after seeing the specific speeds was that this noise is transmission related. The Check Engine Light could be related to your problem, and filling the tank was just a coincidence. Or, the Check Engine Light is related to filling the tank and is not related to the noise. Have the computer scanned by mechanic to see what the code is.

I found a technical bulletin for your car about a shudder, or a exhaust moan at 40 to 45 mph. I’ve heard noises like this before. It’s a resonating noise that can fill the cabin and drown out everything else. It happens at low engine speed, and light throttle application. It is related to the "transmission converter clutch" or TCC. If this sounds like the problem you are having, the fix is an engine computer (PCM) reprogram. It modifies the shifting strategy so it does not "lug" the engine. Your transmission fluid may need to be flushed as well if the reprogram does not entirely repair it. The bulletin number is 06-07-30-30A. Only a Cadillac or GM dealer can reprogram the PCM. If you have an extended warranty, this should be covered. If not, you will have to pay for it, so make a few calls as prices can vary.

If you find that this is not the source of the noise, your best option is to have a mechanic ride in the car and inspect the car noise. If you would like to have an accurate diagnosis before taking the car to the dealer, consider YourMechanic, as a certified mechanic can come to your home or office to determine what repairs are needed.

ANSWER : Hello. Most of the time, this is caused by a failure in the transmission. It may be as simple as a low or contaminated fluid. I usually check the fluid and change it if it is bad. If the fluid is fine or if the issue continues, then it may have a failure in one of the internal bearings. If you need to have this checked, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the whining noise and let you know what should be done.

ANSWER : Hey there, thanks for writing in. I would have a professional mechanic check out the constant velocity joints on your vehicle. One or more of them may be worn enough to cause the noises you describe. S/he can diagnose and replace any failed CV joints.

ANSWER : Hello. Warning lights accompanied with stalling can be caused by many things. If the oil is low I would go ahead and top it off to prevent the possibility of engine damage, however, it is unlikely that low oil is what caused the stalling. Stalling is most commonly caused by issues with the ignition, engine management, or fuel systems. If one of the components, such as a major sensor, the fuel pump, or the ignition coil, go out or have an issue they can cause the engine to stall. If the vehicle is no longer starting then it may be possible that there is an issue with the electrical system as well, perhaps a faulty battery or alternator. If the alternator goes out it will eventually drain the battery, which could also cause stalling. Scanning the computer for trouble codes, once the vehicle is started, will likely reveal some insight into what the issue may be. As the possibilities could be many, I would recommend having a professional technician, such as one from YourMechanic, come to your location diagnose what may have caused your vehicle to stall.

ANSWER : Hi There,
What you are describing sounds like you may have a clogged catalytic converter. The catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When the catalytic converter is clogged, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly. When this happens, the engine is forced to work much harder to expel these gases. This often results in the engine bogging down, hesitating, shaking and causing very poor fuel economy. This should also cause a check engine light to come on as the O2 sensors should be reading the incorrect amounts of oxygen in the exhaust gases if this is your problem. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your catalytic converter.

ANSWER : I have seen this same scenario many times. The problem I believe is from a clogged catalytic converter. When they become clogged they restrict the flow of exhaust gas and the engine can not operate efficiently. I would recommend having a technician, from YourMechanic, to come inspect your vehicle’s Check Engine Light and replace your catalytic converter if needed.

ANSWER : It sounds like you may have a weak ABS wheel sensor and a loose wheel bearing. When you hit the brakes, the sensor losing signal may be causing the ABS to activate. You would need to have the ABS diagnosed to see what sensor is having the problem and to check that wheel bearing and sensor. You may have to replace the bearing and have a sensor replaced in this case. I would have a certified technician, such as one from YourMechanic, inspect the noise in person before moving forward with a repair.