new problem need help

[blazinman08]

i have an 89 chevy s10 blazer 4.3 liter 4wd and just yesterday i started to hear a clunking noise from under the hood so today i went to go start it and it started really hard and then when it idd start it made a horrible clunking noise sounded like a iece of medal was hitting another piece of medal im pretty sure it is coming from the engine cuz the engine shakes really bad. what could this be. i know it has a bad o2 sensor could this be a problem

[Spectria, L1 MT]

Originally Posted by blazinman08

i have an 89 chevy s10 blazer 4.3 liter FWD and just yesterday i started to hear a clunking noise from under the hood so today i went to go start it and it started really hard and then when it did start it made a horrible clunking noise sounded like a iece of medal was hitting another piece of medal im pretty sure it is coming from the engine cuz the engine shakes really bad. what could this be. i know it has a bad o2 sensor could this be a problem

I would not run it it any further until you locate the problem. Most likely not an electronic or O2 sensor problem, possible pulley or major engine failure.

First, look at the vibration damper on the front of the crankshaft, bottom center pulley. See if it looks straight and there are no metal filings around it.

You may need a second hand to check if it turns straight, keep your hands out of the workings, Brake on, in park or neutral, block the wheels. Have competent friend crank engine for a moment while carefully watching the main pulley, then all the others. Post you results.

[blazinman08]

all of the pulleys are fine. my dad said it was a rod knock. now this is one thing i am not sure of. what rod would he be talking about, a push rod? and it doesnt bang on whatever its banging against nearly as bad (bearly hearable) when i rev it up, its kinda like it makes it better when its revd up like that. what could this be.please help asap. junk yard soon.

[Spectria, L1 MT]

Your dad is probably on the right track. The rod he is referring to is a connecting rod from crank to piston. Which one is probably unimportant, as nothing can be done about it without a Major tear-down.

If it is a rod knock don't run it at all, you might be able to save the crank and block.

It could also be a badly worn piston that is slapping as it rocks at the top and bottom of the stroke. It, as well as a "ROD" knock will change with RPM.

This could be repaired with a single piston replacement, but would require pulling them all, cleaning them and weighing them to be sure the new piston is in the proper weight range for the set.

The jury is out on what you should do. If you can afford it, a proper complete overhaul is the right way to go.