I found a vid re: calibrating the sensor; went to the NGK site, it said it might have to be calibrated, check with Chevrolet. But, like I said, there are no new codes and I don't get the sensor code either. Here's what it does: starts good then warms up to I don't know, 185 degs or so and starts missing and may throw the TCL. Let is sit for 20-30 minutes it goes away. Does it earlier and more often without the A/C on, for some reason.

 

Coolant full , no air under the rad cap?

 

TCL ? That’s a new one. Trouble code light ?

 

The crank sensor change was a mistake. You probably just introduced more problems.

I was going to ask if you ever checked the chain tension per Oldblue’s suggestion back in February, but I think you just answered that question.

You probably don’t really need a valve cover gasket. It’s reusable; just make sure you’re careful with it and clean everything.

 

No issues with head gasket. Compression test showed the problem. Cyl 4 was about 90 with no increase when cranking. #3 was 150. As for the crank sensor, like I said, it's acting no different than it did prior to installation. Looks like it's time for a new head. So, suggestions as to the best to get. Going with a loaded head for the new cams. If you can reuse a VCG, then why is it leaking?

 

Sounds like a broken spring. Check the valves before removing the head.

 

Maybe the VCG was damaged when someone else worked on the car.

 

The only codes for the crank sensor are for it being broken or not learned at all (new ECM). In other words: no codes doesn't mean the variation stored is correct. If you replace the sensor without relearning the ECM will continue using the variation it learned from the old one. It is not the sensors fault it is the data in the ECM that needs recalibrating.
The crank sensor is responsible for detecting misfires. If the sensor or the ECM or any wiring connecting them is changed a relearn is needed, fault code or not. Some people are lucky and the old values work with the new parts.
A relearn requires a computer interface like a Tech2. Some shops have them GM shops should have them.

I don't know why you didn't do a (free) compression test before throwing parts around.

 

Post #35 , Donbrew, he did a compression test, #3 , 150 psi, #4 , 90 psi.

To me that indicates a bent valve ( not likely) or burnt exhaust valve.
you don’t really require new cams, you do need to pull the head off and verify the damage, before you order any parts.

 

Low compression in one cylinder calls for a leak-down test.