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Old 11-20-2007, 09:20 AM
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Default 4.3 engine knock

i have a 96 blazer with the 4.3 in it. i just got it so dont know to much about it. all i know is that the engines knocks loud on acelaration. sounds like rods but not sure? the person i got it from had some work done to it thenm it started knocking? so i got it cheap. how can i tell if it is rods or the pistons or ??? thanks,matt
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Old 11-20-2007, 02:42 PM
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Default RE: 4.3 engine knock

What does your knock sound like?Do other people look at you crazy when you ask them if they can hear it?
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Old 11-20-2007, 07:17 PM
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Default RE: 4.3 engine knock

it doesnt do it till you get to the higher rpm. but if you grab the throttle and rev it in park its loud. iyou can feel it through the throttle body when you have a hold of it? feels like its right uder the intake.
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Old 11-21-2007, 01:29 PM
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Default RE: 4.3 engine knock

i found out some more info on my s10 blazer today. it didnt knock untill they replaced the 4 oxogene sensors and the converter? thanks,matt
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Old 11-21-2007, 01:53 PM
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Default RE: 4.3 engine knock

That doesn't sound much like an engine knock. It sounds like that maybe you have a bolt loose on your torque converter housing, which will cause a knocking sound but not cause it to slip under accel. That doesn't exactly mean its not an engine knock, but most of the time an engine knock will be constant at all speeds.
Generally, new O2 sensors and a new cat will not cause knocking, it may make it more noticable because the engine will run with a lot less stress, making the sound more audible. You'll want to start with servicing your transmission.. When you take the tranny pan off, there will usually be a magnet in the bottom of the pan that collects metal dust and shavings, if that is coated with a lot of debris, clean it with parts cleaner or mineral spirits and finish the service. If its a rediculous amount of metal, it can indicate whether you have a transmission problem. Then change your oil. The magnet on the oil plug will pick up a lot of metal shavings if you have a lot of friction.
If neither is the case, you'll want to rebuld the engine. Then if the noise is still apparent, rebuild the transmission and go from there.
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Old 11-21-2007, 04:17 PM
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Default RE: 4.3 engine knock

the converter would make that sound come from under the intake? hmmm. ok ill have to check that out. i was just looking for tips to look at before i pull the engine. the people she bought the car from said the engine had been changed before but not sure if it was new or used? is there numbers on the block i can run to maybe find this out? thanks,matt
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