That's the frustrating part. The engine has not knocked since Monday morning at the dealer. After I turned down the $4200 estimate, I told them to change the oil anyway (even though they insisted it was a waste of money since my engine was about to die). When I picked it up, there was no noise.
Every day since Monday I have driven it and NOTHING.
But that is typical. I cannot pinpoint what makes it knock and/or why. It never knocks on start up and even if I drive it 20 minutes or something, it doesn't mean it will start knocking. Sitting in traffic has little effect. But sometimes, I will be driving along and I can hear it and if I roll down the window and turn off the a/c, it's pretty loud.
I drove it 5 miles on I-95 last night and got nothing. After I read your post suggesting I record it, I just took it out and drove around and got ZERO. Oh, it will do it again. I will record it. But I cannot "make" it knock.
One other additional, perhaps unrelated note. From time to time the service engine soon light comes on and I get a P0172 and P0175 code. I don't run to the dealer because I looked it up and after asking everyone I know who even remotely knows anything about cars, most agree it's probably related to the fuel injectors.
I also found an old Chev technical bulletin that mentions PO172 as an error code.
But...after the car sits overnight it goes away. The last time I got the codes was February.
Again, I don;t know if something is really wrong with my engine and I don't know if my lifters have collapsed. However, if so, they are pretty damn quiet over the last few days.

 

how is the oil pressure? does it change when the noise happens? obd2 code list is here https://camaroforums.com/forum/93-02...i-codes-57023/ moved your thread to the 4th gen general section for you.

 

those are both rich condition codes. how old are the 02 sensors?

 

On June 15, 2015 I took to the same dealer because it was throwing code P0162-the O2 sensor. They replaced Bank 2, Sensor 2.

 

sensor 2 on both sides are for measuring the effectiveness of the catalytic converter. sensor 1 on both sides are for providing information to the ecm/main computer so it can do its job, the number one sensors are between the converters and the exhaust manifold. side one is on the same side at the number one piston or the driver side. two obviously is on the passenger side. rich condition can come from several things, cylinder not firing, sicky injector not closing, 02 sensors failing, fuel pressure low, fuel pressure high, temp sensor failing and a few i forgot.

 

I find it funny that they told you this,

Yet you've been driving the car with zero issues. Fairly certain that if they were that bad, the engine would have been ruined by now.

Another thing I noticed, $1700 in parts alone? What the hell are they all replacing? A complete gasket set from the heads up can be had for under $150. Lifters would be another $100-150. A new cam would only be a few hundred bucks. They could replace the oil pump but that's maybe $200 for a upgrade unit. My math isn't great but I'm seeing maybe $800 in parts, less if you do only the lifters.

20 hours labor? Not a chance. We did my cousins cam swap in less than 5 hours. Granted two people working is faster than one but we also took food breaks and were drinking beer

 

When they told me not to drive it, I will admit I was momentarily frightened. But when they brought it back and it wasn't knocking and the engine sounded the way it always sounds, I was fairly certain they were full of it.
I did not get an itemized list of parts and I had already checked the list price of lifters and some of the other stuff that I thought they might have replaced, so I knew that even for a dealer, the cost was ridiculous. But I could almost swallow that mark-up.
But 20 hours of labor? I mean, who agrees to a $4,200 repair bill without taking it for a 2nd look someplace? Last year I spent about $3,500 at the same dealership for 3 jobs - replacing power steering hoses, O2 sensor and repairing the rear main seal and related stuff. I think maybe I was TOO GOOD of a customer. They got greedy.

 

You had mentioned you have an exhaust leak, I addressed this earlier. One possible cause for PO162 is a hole/leak in the exhaust. O2 sensor isn't the only possibility, but could be a better money maker for the dealer. Get the exhaust leak fixed first before assuming it's anything else. This whole issue (error code and noise) could be caused by something as simple as a well placed exhaust leak. You need to eliminate that variable.....unless you enjoy draining your wallet.

 

There's no question that I have probably paid more than I needed to and relied on dealers and mechanics with barely disguised motives. However, I have consistently taken care of the care, based on the recommended maintenance, since the day I got it. I have every receipt for every oil change, every repair, etc. and only abandoned the owners manual with the records pages when I broke 100K. There's not a mark on the body and I don't necessarily ignore warning signs. But I do get stumped. I work in the IT industry, specifically RFID and related technologies for manufacturing, but I am not a mechanic.
I value the opinions you've given me and I am going to take your suggestion and approach it as an exhaust leak. No, I am never going back to that dealer. I have a year old Sonic that I bought when I decided the Camaro needed to become my second car and I won't even take the little Sonic the dealer now, even though it's under warranty.
My challenge, of course, is finding a mechanic. I only ended up at the dealer after getting nothing but conflicting advice and big bills from independent shops.
If I can ask you one more thing--could it be the catalytic converter? I talked to a couple of guys at a car show recently who both had my Z28, but with higher miles and they mentioned it. I don't even want to hint at that to a mechanic.

 

?you run 93 octane