Hello

I have a 2002 blazer with 70,000 miles well maintained. The engine started knocking. Im getting a multi cylinder misfire jumping from cylinder 2 and 6 and at times others as well. The knock is very faint at 1500 RPM which increases as the RPM's go up. It is steady. I was told that the knock sensor is causing the missfire problem. But I read that a misfire problem could cause an engine to knock. Can this be? Or does this sound like a bad bearing or something? New plugs, wirers, cap and rotor. I read on this forum that a bad distributer could cause the misfire. Some sort of treatment from GM was put in the intake to clean carbon build up, which did nothing.

Any advice would be great.
I was told the motor needs a rebuild.

Thanks

 

Your bad knock sensor would sound like a rattling on acceleration. A bad distributor not advancing may lead to this. A tick, tick, tick might point to a lifter failure. A wap or knock could be a spun bearing. Do some things that don't cost you money first. Swap wires to see if the misfire travels.

 

I agree with Chevy33 points. How many miles have you had the vehicle and how long ago did the knocking start?

 

I just got the truck. It was given to my wife a couple of weeks ago. We were told it had a misfire code when it was given to us. She drove it a few miles when the knock started. (on the way to my brother inlaws auto body shop) It did not have a knock when we were given the truck. I checked it out pretty good. Reved it up a bit and held it there for a few with my head under the hood. Im thinking its a mechanical problem because the knock stays steady and not just on acceleration.

Any good rebuilders online I can order from? I found a bunch, but who to trust?

GM wants $2200 for a new long block. Labor is not much of an issue i have a shop I have full use of.

As stated above new cap, rotor, plugs and wires.

 

You seem eager to buy the cart before the horse. You refer to this as a knock. A knock is serious. The people here can guide you in the correct direction if you participate. Your assistance by means of giving better description may help us help you. Just because you have new parts does not guarantee that all is well with those parts. I for one prefer to diagnose the problem before throwing money around. Help us help you.

 

I agree with Chevy33. We bought a used engine so did not need a core engine but if you need a core engine to cut costs then you do not want to drive it until it is trashed beyond being good for a core engine.

Knock is a subjective term and the cause needs to be determined.

Has it been ran with water in the oil, just have a distributor cap that defective/off brand, etc.