Thread: engine noise

I have a 97 f150 4.6 and when I'm towing a load and accelerating a little harder than normal like to climb an incline or just to speed up I have a bad crackling noise coming from my engine. Its the same noise it would make if I was low on coolant or oil but I'm not. It also does it climbing an incline when I'm not loaded just doesn't sound as bad... any thoughts?

Does it sound like marbles are rattling in the engine ? Could be spark knock.


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It does sound like marbles in the motor. How do I fix a spark knock?

There is a lot of things the can cause spark knock. Bad fuel, aggressive tune, mechanical issues with motor, and carbon build up on the pistons.
Make sure you have a stock tune and see if it does it.

What I would start with is do a compression check. See if one bank has more compression as compared with the other side. Sometimes the chains guides wear out or break causing incorrect valve timing which can cause spark knock in some cases. If that's fine. U can do a de-carb. Ford has some cleaners u can use to clean carbon build up. It may take a lot if bottles. In some cases we have used about 7. I'll get u the part number on Monday as I left work. But u can go to a ford parts counter and ask. They only have one type.


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OK great. Keep in mind I have to do all this myself do to Xmas messing my wallet up a little bit ya know. This is the only transportation I have for my family so I have to keep it going. Every little thing that goes wrong with it I get worried. Where can I get the compression tester at? Does the parts store loan them out along with the other tools?

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O one more thing I forgot to ask.... will a spark knock hurt my motor?

Don't think parts store will lend them out. U can pick up a set at harbor freight if there is one near u. And yes. It can break a piston.


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Also check for low fuel pressure at wideopen throttle. Should be 40 psi at wot


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OK. I'm gonna check the fuel pressure tomorrow. When I connect the gauge on the valve what do I do then?