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Death rattle!

Hi, I was told by the dealership mechanic that I have a “death rattle” in my Ford F-250. The check engine light came on about 3 months ago for a miss fire. I replaced the plugs and coils on both misfiring cylinders. Light gone. It came back on yesterday, so I took it in. They told me it was a miss fire, and that the rattle I also reported hearing was the so called “death rattle “ . To me it sounds like a loose heat shield in the front of the truck, but I only hear it when I hit about 2,000 RPM, and it’s especially loud when I’m hauling heavy loads.

Is this a thing? They couldn’t even tell me what’s exactly wrong, just that they could fix it for $4 k, and it would eventually still fail, or put a new engine in for $7k. 5.4 L engine

Since you are to pay for this get a second opinion . And what does Death Rattle mean anyway?

When an engine develops a hard rattling ‘knock’ under a heavy load it is often caused by one or more main bearings failing. But then detonation would occur under the same driving condition and it’s difficult to distinguish sounds from descriptions. If you haul a heavy load with a tank full of premium and the noise doesn’t occur you might need to blow out the carbon to prevent detonation…

Concur w/RK above, most likely either loose bearing (rod knock), or detonation. No way to tell, but if the dealership mechanic calls it a “death rattle”, probably is. They hear all sorts of sounds from the cars they service, and are able to interpret sounds much better than somebody without that experience. Still, it makes sense to do some experiments to prove or disprove the detonation theory. Experience with different brands and grades of gasoline, verify the ignition timing at idle is correct and does what it is supposed to do off idle. I’d replace all the plugs, verifying the gap is correct in all. While the plug are out, measure the cylinder compressions. If you think it is a heat shield – which is possible – you might could use a length of garden hose as a stethoscope to see if you can isolate where the noise is coming from. I have a 1970’s Ford truck and one time I got a vacuum hose connected to the wrong spot, and the result was, it sounded like the engine was a big can of shaking rocks at first start-up. Timing was incorrect.