7.3 unusual knock - detonation?? - Ford Powerstroke Diesel Forum
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Old 11-16-2007, 08:33 PM
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7.3 unusual knock - detonation??

Noticed lately (colder mornings) during light acceleration heading out on the road that I can definitely detect an intermittent knocking sound, which sounds to me somewhat like detonation on one or more cylinders. Its not the usual diesel clattering sound, which is more rythmic in nature, but rather more of an intermittent knocking during light acceleraton when the engine is not to full operating temp. Its not as noticeable after the engine is at normal operating temp. but i think I can still here it a little when I accerlerate after stopping or slowing down. It's not noticeable at cruise.

Sure wish I could record and post the sound i'm hearing but I guess my description will have to do.

Any ideas? I've not had it scanned for codes - no CEL/SES indications. 120K miles on it with no other problems, did change the fuel filter but no change. Have been using Power Services for about the last 4 or 5 tanks. Have also noticed a drop in fuel mileage but my driving
habits have not changed.

Injectors going bad? Low fuel pressure?
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Old 11-16-2007, 09:01 PM
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mine was making the same sound a few days after i bought it. took it to the dealership and they said it was because I had bad fuel. BUt it did it again 2 days ago when the tank got at a 1/4 of fuel.
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Old 11-17-2007, 05:17 AM
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engine knock-vibration

I had the same problem when i got down to tank, so now I fill up at tank, no more problems. bad tank sender? check threads posted by RCFlyer on this problem. I have a '03 PSD 7.3 hope this helps.
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Old 11-17-2007, 05:24 AM
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I had this problem as well. Truck started acting like it was running out of fuel at 1/4 tank. I ended up dropping the tank and cleaning the pick up tube in the tank. The fuel screens in the pick up tube were nasty looking. Now my problem is gone. By the way I have 156,000 miles on my 2002 F-250.
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Old 11-17-2007, 06:59 AM
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Does it sound like this?

how cold is the weather?

Usually cackle is only at idle though, but the catalyst of cackle could be the same thing as to why you're hearing a sound. Probably just nature of the beast with the cold weather.

There could always be multiple factors at play, winter fuel? engine oil weight? etc. etc. etc.

Some of it may have part in paranoia imagination, everyone gets it.
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Old 11-18-2007, 05:45 AM
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Looked at all the threads on the issue and I'm thinking it must be the nature of the beast. I can't detect it at idle but only on easy to moderate acceleration when the engine is cold (OAT 50-ish or less). However, when I accelerate hard with a cold engine I don't hear it. It's got me puzzled! Once she's warmed up it seems to go away or is lessened to the point of being almost undetedible.

Listened to your vid at idle and yours sounds pretty much like mine, which seems normal to me for that infamous diesel cackle.

I might try to do a sound clip of mone from the cab while driving to see if it will pick-up and record the sound I'm hearing. Will post if successful.

Thanks for all the input. It may well be just paranoia, since I'm new to diesel ownership.
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Old 12-01-2007, 07:02 PM
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I think I'm hearing the same thing, but It might just be in my head..
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