Knocking noise under load
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Knocking noise under load
This will be my first post, a big Hello to all of the fans of this web site. I hope to get many useful tips. With that said, I have a 1992 F350 dually with the 7.5 litre, 460. My problem the last few times out with my boat in tow, I have noticed a knocking noise when pulling hills. The noise only makes itself known when engine is under load. I have checked the timing and everything seems to be ok. I am also running 91 octane so I dont think its the gas. Any thoughts?
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From: Albuquerque
Welcome to FTE!First, why are you running 91 octane??? Unless you have modified your 460 in anyway...it is just a waist of money on fuel. What happens when you use a higher octane it burns slower, which if the engine is not designed to burn it at that rate...you will get a ping/knocking sound.
Have you modified this 460? How many miles? When was the last tune up (spark plugs, wires, dizzy cap, etc.) I would suggest pulling a couple of spark plugs (one from each side) and see how they look. Go back to regular unleaded gas. See how the 460 runs. It will take a few tank fulls to get an average.
Just to start off...but I am sure more folks will chime in.
biz
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
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He probably went to 91 when the pinging started. That is what I did with my V10, I switched grades to try and stop it. Other than checking air and fuel filters on a 92, I dont what else to tell you.
Is the truck an auto? Does it seem like its trying to hold the wrong gear for the work you are doing? What RPMs are you turning when this happens?
Is the truck an auto? Does it seem like its trying to hold the wrong gear for the work you are doing? What RPMs are you turning when this happens?
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Madmedic is correct, I started running 91 when the pinging first started, seemed to help at first. Have not modified engine at all. Has 165,000 on motor. I buy all my tune up parts from ford so its running with what the factory calls for. I have noticed some carbon build up inside the distrubitor cap, seems excessive to me. Sometimes when driving it feels like its really hooked up and strong, other times feels very sluggish. Is it possible that I have a short of some kind? Fuel filter is new, from ford.
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From: Albuquerque
You mentioned that you checked the timing...so what is it set to?
Do you only get the knocking when towing? Or is it all the time?
I think it is possible to have a short at the dizzy or from the spark plug wires. You didn't mention when your last tune-up was (year and mileage)?
biz
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
Do you only get the knocking when towing? Or is it all the time?
I think it is possible to have a short at the dizzy or from the spark plug wires. You didn't mention when your last tune-up was (year and mileage)?
biz
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
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Check the EGR for proper operation.
The EGR recycles some exhaust gas, lowering combustion temps. A side-effect of this is reducing pinging. If the EGR is clogged, or the diaphragm cracked so that the valve isn't working, or you have a cracked vacuum hose going to it, anything that impedes the EGR, it will ping.
However, I wonder if the "knock" is really a ping?
The EGR recycles some exhaust gas, lowering combustion temps. A side-effect of this is reducing pinging. If the EGR is clogged, or the diaphragm cracked so that the valve isn't working, or you have a cracked vacuum hose going to it, anything that impedes the EGR, it will ping.
However, I wonder if the "knock" is really a ping?
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From: Pennsylvania
I agree with Krewat,check your EGR valve.It's possible to clean it up some,the carbon can be chipped away.Until you can purchase a new one,just try not to damage the gasket.
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It has been two years since I have had it smogged, so I guess it could be the EGR valve. I am pretty sure it is a ping, only has been happening on the up hills under tow. I tow a 28 foot Bayliner Cierra Sunbridge. Fully loded for the week end will weigh out around I think between 8 and 10k. Flat roads no noise. Only hear it the ping when you really start to put the gas to her. Baffled. Will have the egr checked and see what happens. Have thought to drop it off at ford and have them analyze it but that wouldnt be as much fun, and probably a lot more expensive.
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Brett Foote
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From: Long Island USA
Sounds like EGR. Find the EGR valve vacuum hose, apply suction (with your mouth on a new hose, if you have to 
) when the engine is idling. If as you suck on it, the idle doesn't change, the EGR is not moving or it's clogged.
By the way, why are we talking about a 1992 460 in the Superduty forum?
) when the engine is idling. If as you suck on it, the idle doesn't change, the EGR is not moving or it's clogged.By the way, why are we talking about a 1992 460 in the Superduty forum?
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From: Albuquerque
Originally Posted by krewat
By the way, why are we talking about a 1992 460 in the Superduty forum?
biz
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Carbon build up in the distributor cap??!!
There should be none. If the inside of your cap has carbon, it is time to replace the cap or at least clean it out. This can cause missfires and maybe pinging or knocking and poor performance. Disty caps are a regular maintenance item that most of us ignore. It probably should be replaced every 50K miles or so.
Might also mean that the disty itself might need lubrication. I think there is a cap in the top of the shaft that covers the area where it needs oil squirted every once in awhile. I could be wrong here since I have been lazy myself and not done this. If there is a rubber plug or cap, look down inside. If you see a felt pad, that most likely means you need to squirt a few drops of light engine oil in there every 12K miles or so. I even think I saw a reference to this in one of the shop manuals. Wild guessing is that this isn't as important as back in the days with mechanical timing advance weights in the disty, but I think it is still there.
With 165K miles there are a lot of things that could be causing knock. Carbon deposits are the usual culprit, and loose timing chains, sticky EGRs, old plug wires etc.
Also worth checking fuel filters. This is one of those things that goes bad very slowly to the point you don't notice until it is a big problem.
Good Luck,
Jim Henderson
There should be none. If the inside of your cap has carbon, it is time to replace the cap or at least clean it out. This can cause missfires and maybe pinging or knocking and poor performance. Disty caps are a regular maintenance item that most of us ignore. It probably should be replaced every 50K miles or so.
Might also mean that the disty itself might need lubrication. I think there is a cap in the top of the shaft that covers the area where it needs oil squirted every once in awhile. I could be wrong here since I have been lazy myself and not done this. If there is a rubber plug or cap, look down inside. If you see a felt pad, that most likely means you need to squirt a few drops of light engine oil in there every 12K miles or so. I even think I saw a reference to this in one of the shop manuals. Wild guessing is that this isn't as important as back in the days with mechanical timing advance weights in the disty, but I think it is still there.
With 165K miles there are a lot of things that could be causing knock. Carbon deposits are the usual culprit, and loose timing chains, sticky EGRs, old plug wires etc.
Also worth checking fuel filters. This is one of those things that goes bad very slowly to the point you don't notice until it is a big problem.
Good Luck,
Jim Henderson
Last edited by jim henderson; Aug 16, 2006 at 04:52 PM.
