We have a '95 S10 Blazer with the 4.3 vortec. When I purchased it the vehicle idled really rough. The engine light was on so we took it and had a diagnostics done and it gave us the upper o2 sensor was low voltage. I have just changed the plugs, wires, cap and rotor, air filter, fuel filter...the engine has a ticking noise in it when you first accelerate or when you let off the gas, once you get going down the road you won't hear the ticking unless you let off the gas. The oil was pretty crappy when we bought it and it didn't tick until after we got it home. Lifter? Could that be all junked up inside? Did have the engine flushed when we changed the oil. Engine has 105,000 miles, nothing was ever changed on it, all still factory. Whoever was previous owner didnt' take care of it maintenance wise

 

Sounds like you have an exhaust leak and based on the information provided, it is located between the engine and the upstream O2 sensor. An exhaust leak before the O2 sensor will make it read lean (low voltage) as outside oxygen gets introduced into the exhaust stream. Areas to look are at the gasket between the exhaust manifold to head and the donut gasket between the exhaust manifold and the y-pipe. Check these areas on both sides.

 

took the blazer to a couple of dealers and one private mechanic, all have said it sounds like a ristpin? The ticking just started within the last week. Could it be a stuck lifter?

 

I had a 2.8 with the same noise come to find out the flex plate was cracked check it

 

Nope not a flex plate. I'm thinking a lifter? Been told it's a ristpin? When the engine is cold it won't knock, but after it gets warm it will. Sometimes it will quit around 40mph. and other times it will just do it when you accelerate or let off the gas a little...