I have about 116k miles on my truck. For a while i would hear what sounds like an engine rattle if it had been recently started when accelerating in the lower gears. For about the last 8-10k miles or so, I am hearing it upon ignition for just about a second or so. Mechanic shop down the street says it is nothing to worry about and common with this truck. A former mechanic I crossed paths with says it is either cam phasers or bad pcv valve. He actually approached me whengetting into his truck after hearing mine start up. At start it literally sounds like marbles or small rocks churning in a metal box.

Has anyone had any experience with this? I recently had spark plugs replaced and it seems a little better when driving but still rattles at startup. Not sure if that would have anything to do with this. I have also always been on top of oil changes, although there is some burnoff between changes (but no leaks), which I have heard is normal for this mileage.

Any info or advice would be much appreciated. TIA

Is it a rattle or knock?

My 2018 with 5.0 had a loud knock while running that turned out to be the cam phasers. If your noise only last a couple of seconds, might not be much of a problem. Has anyone put a stethoscope on it? Hard if it doesn't last long.

Would a PCV valve really ever make that kind of noise?

1agswitchin4lanes said:

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Is it a rattle or knock?

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I would definitely describe it more as a rattle than a knock. It's not uniform in rhythm. It's kind of sporadic during acceleration, not an evenly sounding rattle.

If I start the engine cold after sitting for hours, it's sounds normal at ignition, followed immediately by a 1-1.5 sec rattle sound…but I could see someone describing it as a knocking sound TBH.

Sorry, not much help I know

Timing chain tensioner? Mine failed (1 of the 2) on my 2007 Tundra 5.7 and I replaced it myself. I haven't heard of them failing on the Fords though. Cam phasers are definitely the most likely culprit.

Following, but sounds similar to what my 2010 Ram 1500 5.7 does.

It it's a knock then 2 bottles of LIQUI MOLY Oil Additive Cera Tec 20002 Ceramic Wear & Tear Protection every oil change.