Engine knock when cold on acceleration
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Joined: Oct 2003
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From: Baltimore
Engine knock when cold on acceleration
I have a engine knock on accelertation when the engine is cold. It sounds like a rod knock. When the engine gets to normal operting temperature the noise seems to go away or at least is less noticable. The engine has always had the knock, but recently it seems to be getting louder and on occasion it can even be heard when the engine is hot. I suspect a bad injector. Any other ideas? I thought it might be crackle, but the threads I have read indicate crackle occurs when the engine is hot and can also be heard at idle. Mine is when the engine is is cold and under load or on acceleration.
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From: Baltimore
I called the dealer today and spoke with the service advisor. He said it sounded like it could be the exhaust back pressure valve. Maybe, but I thought the valve only activated when the air temp was like below 42* or so. This one does it summer and winter, just seems to be louder with colder temps. He also said a bad injector it would set a code. I haven't seen the "check engine" come on, but I'm going to check for codes anyway. I think the back pressure valve goes to open default if the sensor is disconnected. If there aren't any codes, I'll give that a try.
Postmaster
Joined: Aug 2004
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From: SHELTON, WA
or that cylinder isn't firing until its warm how about that?? how cold is it up there right now? i had this problem last year. bad gp's were the cause. once it was warm it ran sweet but cold the exhaust was just dwonright unbearable form raw unburnt fuel. do you get a lot of white smoke on startup?
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From: Baltimore
It's running smooth. Every once in awhile, during the warm up when it's knocking, there is a little surge. Sort of like a gasser with the EGR valve working. I had the HX mod on and it idled real smooth. Took it off. It didn't affect the noise one way or the other. Night time temps in the upper 40s to mid 50s. The exhaust doesn't sound like it would if the EBPV was kickin' in.
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From: Baltimore
I've heard of piston cooling jets falling off, but don't know what the symptoms are other than finding parts in the oil pan. Does the engine make any noise if one is missing? Could my noise be from one missing causing the piston to run dry when cold, and as the engine warms ups the piston expands, and splashed oil reaches the cylinder walls? I'm hoping for something simple, but my luck doesn't usually go that way.
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Spoke to the dealer tech today and he said it sounds like it might be an injector. Because it only happens after a cold start and has to be under load it would be hard to determine which injector is making the noise. He suggested I continue driving until it gets worse or can be heard without driving the truck. I'm going to stop using a fuel additive for awhile and see if that makes a difference.