Magnum 5.2L Whining noise
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Magnum 5.2L Whining noise
My 01 Ram 1500 with Magnum 5.2L when at heavy throttle gets a almost supercharger whine to it. Happens around late 3k Early 4k rpms and sounds just like a supercharger blower. Any idea what this could be?
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Joined: May 2019
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From: S.W. Indiana
Maybe it doesn't like working so hard.
Seriously, it could be a bearing, your fan or something with the air intake. Like Moparite mentioned, start by pulling the belt off and race the engine. Just for a moment as the belt also runs your water pump to cool the engine. However, with the belt off, now would be the time to wiggle all the bearings and your water pump fan. If nothing wiggles and the whine goes away, get a wooden dowel rod about 2 or 3 feet long. With the belt back on and the engine running, you can listen to each accessory in turn. There is a cartilage flap on your ear opening. Press that closed with your knuckle and then put the rid against your knuckle and place the end on, say the alternator. This will let you hear any noise from a failing bearing. If your alternator for instance is begining to fail, you can replace it before it packs it in and heads south. 
Might try pulling the front Oxygen sensor connector and seeing if the sound goes away.
By UnregisteredUser: "The hissing is almost universal when that sensor fails. It's caused by the IAC being fully open as the PCM tries its best to get the idle speed back up to normal.
In most cases it starts out as a stumble that lasts just a few seconds when the PCM goes into closed loop mode. Over time the stumble becomes more pronounced and lasts longer, then eventually the failure progresses to extremely low idle speed and hissing intake upon transition to closed loop. Let it go still further and the engine will intermittently lose power on the highway at cruising speed while the truck is unladen. Until just about the very end, you can open the throttle to get the engine speed up so more hot exhaust gas flows over the sensor to heat it and get it functioning more or less normally.
Y'see, an end of life oxygen sensor reads rich, and the more it decays the more falsely rich it reads. So at the appointed time the PCM goes closed loop and starts paying attention to the oxygen sensor, and it sees a false rich condition. It narrows the injector pulse width to compensate, which lowers the idle speed, and when the PCM sees the RPM drop it starts stepping out the IAC to compensate for that. This drives the mix still leaner, but until the PCM sees that via the O2 sensor it doesn't react because the TPS is not giving an indication that the throttle is opening -- thus the transition stumble. In the early stage of the failure it'll find a happy medium pretty quickly, but as the decay progresses the PCM is getting an increasingly inaccurate picture of the world. Eventually the problem reaches the point at which the PCM goes closed loop to find what looks like a gonzo rich condition that calls for the shortest injector pulses it knows how to throw, which requires the IAC to be stepped out to wide open. Hisssssssss....
The easy test: Unplug the sensor to force the engine to stay in open loop. If the symptoms stop, the O2 sensor is almost certainly bad because that's the one big difference between open and closed loop: The PCM starts paying attention to that sensor.
This is the time of year when we'll start seeing lots and lots of failing oxygen sensors because the weather is cooling. Fall and early winter are oxygen sensor and heater core season."
By UnregisteredUser: "The hissing is almost universal when that sensor fails. It's caused by the IAC being fully open as the PCM tries its best to get the idle speed back up to normal.
In most cases it starts out as a stumble that lasts just a few seconds when the PCM goes into closed loop mode. Over time the stumble becomes more pronounced and lasts longer, then eventually the failure progresses to extremely low idle speed and hissing intake upon transition to closed loop. Let it go still further and the engine will intermittently lose power on the highway at cruising speed while the truck is unladen. Until just about the very end, you can open the throttle to get the engine speed up so more hot exhaust gas flows over the sensor to heat it and get it functioning more or less normally.
Y'see, an end of life oxygen sensor reads rich, and the more it decays the more falsely rich it reads. So at the appointed time the PCM goes closed loop and starts paying attention to the oxygen sensor, and it sees a false rich condition. It narrows the injector pulse width to compensate, which lowers the idle speed, and when the PCM sees the RPM drop it starts stepping out the IAC to compensate for that. This drives the mix still leaner, but until the PCM sees that via the O2 sensor it doesn't react because the TPS is not giving an indication that the throttle is opening -- thus the transition stumble. In the early stage of the failure it'll find a happy medium pretty quickly, but as the decay progresses the PCM is getting an increasingly inaccurate picture of the world. Eventually the problem reaches the point at which the PCM goes closed loop to find what looks like a gonzo rich condition that calls for the shortest injector pulses it knows how to throw, which requires the IAC to be stepped out to wide open. Hisssssssss....
The easy test: Unplug the sensor to force the engine to stay in open loop. If the symptoms stop, the O2 sensor is almost certainly bad because that's the one big difference between open and closed loop: The PCM starts paying attention to that sensor.
This is the time of year when we'll start seeing lots and lots of failing oxygen sensors because the weather is cooling. Fall and early winter are oxygen sensor and heater core season."