Chevrolet: Tapping in engine, knock sensor, valve job

Question
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Followup To
Question -
I talked to Van last week about this, I have 1 1994 Chevrelet Corsica V6-3.1 , which had a tapping noise in the engine since i had moved with it 15 month's ago accross country, I figured it needed a value job, I wrote in to ask about this, and Van said that it probably didn't need a valve job, but just lifters, because the engine starts and runs smooth and there was no visable smoke coming from the tail pipe and no other matter in the oil. he also mentioned that the knock sensor could be malfunctioning, I took it in an sure enough, all it needed was lifters, and they repaired that along with some coolant leakage that he said was present, changed oil, spark plugs, heater hose connection, manifold and value cover gaskets. But they said it still had a tapping in it that they can't pin point, I mention what Van said about a "Knock Sensor" and they said my car didn't have one, they cannot determine where this knocking/tapping is coming from, after all that work on it, what does it sound like to you?
Answer -
Hi Linda, i think you should find another mechanic. Van was right your car does have a knock sensor, and you should have it checked. This type of problem is hard to diagnose without actully hearing the engine. I suggest you ask around for someone who has had a simular problem, and ask them to recommend a reliable mechanic. An experienced mechanic should have no problem to diagnose your problem.  The dealer is a good place. I hope this helps. Regards, Keith.

Keith
didn't go to dealership, to crowded.
Went to another repair shop, they said the knock sensor wouldn't make that kind of noise, they determined it was coming from the lower half of the engine, and I needed a new engine, this engine runs like a brand new one, it just has a slight knock, i can get into it and it will crank the first time and run me all over Tucson without running hot or burning alot of gas, i thought cars that needed a new engine would smoke and run rough and would hardly start. Maybe I'm wrong, this thing has been doing this for almost two years now, and it is still running good. Got any more advice?

Answer
Hi Linda, if its in the lower half it has nothing to do with the valves, you just spent a lot of money for nothing. The knocking in the lower engine is a bearing  and it may stop running at any time and it could run for months. there is no way to know. so you have three options. you can have another engine put in, or have that one rebuilt, or run it until it dies and then decide what to do. The engine can still be bad without smoking or running rough. I hope this will help you. If you need more info just let me know. Regards. Keith.