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Engine Knocking Noise

My mom has a 1991 Chevy Lumina Apv Van. It's running okay right now but it is knocking. When she cranks the car to start it, it doesn't make that noise but when she starts putting on foot on the gas pedal to go that is when the knocking starts. She has a V-6 engine in it.



I'am no mechanic but it sounds like it may be coming from the engine. It cranks right up with no problem, the only time the knocking noise comes into play is when she gives it gas to go.



I'm hoping that somebody can help her diagnose this problem so she can get it fix asap. I have 2 handicapped brothers that have to ride in the van. If you'll need any more info just ask me. Thank you for your time and god bless you'll.



Best Regards,

Chris
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Comments

  • edited November 2010
    "Knocking" describes too many different kinds of things, and if it isn't apparent while the van is just sitting at idle then I wouldn't guess first at the engine. What happens if you just sit in park and rev up the engine without any motion? What happens then? If it "knocks" even when not moving is it more like a thunking or more like a ticking? (Has anyone at least checked the oil?)
  • edited November 2010
    I appreciate your answer but I'm sorry to say I didn't understand it. A guy my mom know's change the rod barrings in it the other day but it still is making that knocking noise. What I was saying was when she turns it on, it doesn't make a knocking noise. It only makes the noise when she gives it gas. She try driving it the other day but when she got about 2 blocks down the rode the van died.

    To answer a couple of your questions; when she just turns it on and just sits in park and rev up the engine, it makes the knocking noise. It sounds more like thunking noise.
  • edited November 2010
    What was there to not understand? There are lots and lots of different noises that can be described as a "knock" - just saying "knocking" isn't descriptive enough to have complete strangers with no access to the car give well reasoned advice.

    That said, if it is more like a thunking and it is present without having the van moving at all then the engine probably needs more than rod bearings - which was an odd thing to leave out of your initial post. Presumably the rod bearings were supposed to fix the knock? If you hang around and stick your head in various places can you tell where the knock is coming from? Up top? Down low? Left/right side?

    One thing you could do is go comb Youtube for videos of engine noises - find one that acts just like your mom's van and post a link.
  • edited November 2010
    It is not advisable to have someone do major surgery on the bottom end of an engine who isn't able to diagnose the noise that prompted the surgery. Those of us who read posts here are limited to the information as can be gleaned from them. And if the engine died as a result of seizing, subsequent to the knocking, further speculation here is futile. If you attempt to start the engine and it will not 'turn over', it is likely beyond hope.
  • edited November 2010
    sometimes with an old worn down engine, the rod bearings can be replaced and that will extend the life of the engine a while. But, if the wear between the rod bearing and the crank journal is mostly on the side of the journal, no such luck. "Knocking" is a technical term, and means the rods or rod bearings are worn to the point where they knock against the crank journals instead of turning smoothly. Unfortunately many people with no special knowlege of engines will call any noise a knock and that makes it difficult for anyone who cant hear the noise to tell you what is wrong. I suspect, from the age of your van, that the crank journals are worn, and it needs to be turned, and oversize bearings installed to fix the the noise problem.
  • edited November 2010
    Have oil changes been done on a regular basis? I mechanic opinion is certainly in order, but at least check the oil level, let us know how the oil looks.
  • edited November 2010
    Are you saying the rod bearings were changed but the noise is still there? any chance you got a look at those old bearings? were they obviously worn out? (did they look copper colored?)any report on the condition of the crankshaft?
  • edited November 2010
    Start looking for a replacement vehicle..
  • edited November 2010
    Sounds like the engine had problems before and a hope and pray set of bearings was just not enough to pacify it. My vote is with Caddyman; it may be time to say goodbye to it.
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