The ususal suspect on the 606 is carbon. The valve springs are pretty light
for those valves, and when you r&r the intake or plumbing, carbon can tumble down and get stuck on the valve seat. This causes a heafty compression leak and misfire.
The compression pops are what you are hearing..."knocking."

The non turbo 606's are cool, because you can sit there and watch them run with no intake manifold.
If you do have a leaking intake valve, finding it with the intake off will be easy, rev her up and watch for sparks getting past the valve. That will be your carboned up valve.

Beware of the busted chunks of plastic fuel line retaining clips. They love to fall into open ports when pulling the intake. That will be a BIG knock that does not go away when rev'ed up.

Regards,
Dr.Diesel

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Dr.Diesel -
Shop Foreman
Master Guild Mercedes-Benz Technician.

Think the dealer is expensive? Do you know how much it costs to train a dealer tech? Or buy the required MB special tools to have on hand?

I have similar symptoms.. Dr. Diesel.. how do you reccomend blowing out the carbon in the head? I cleaned my intake and EGR a few months ago.

Well, with a few months of driving, the carbon should have gone away by now. It usually goes away after 20-30 minutes of driving. Quicker if you drive harder. You may have some other issue in there.
Does it misfire or stumble?
Possible bad injector or valvetrain noise.
Carbon will blast out of there with the first WOT full speed acceleration run in
most cases.
I hope nothing fell in there with the intake off.

Dr.D

__________________
Dr.Diesel -
Shop Foreman
Master Guild Mercedes-Benz Technician.

Think the dealer is expensive? Do you know how much it costs to train a dealer tech? Or buy the required MB special tools to have on hand?

It only misfires on a cold start below 40F for about 2 minutes. But I have a very loud "injector knock".. It goes away while running diesel purge through the system, but comes right back on straight diesel.

John have your girlfriend start the car and start cracking the injector lines. When you trace it down to one injector swap that one with another and make sure the problem follows it.

Then just send that injector out and have it rebuilt, or order a rebuild from Phil. That way it will only cost you a couple of bucks to fix it.

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2016 Corvette Stingray 2LT
1969 280SE
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