Hello. 30 years under the hood professionally, First time in an automotive forum. Got a tough one.
99 Silverado 4.3 VIN W 132K miles, well taken care of.
Symptom: A little rough at idle, not bad enough to set a specific cylinder misfire code. Maybe one miss every 2 - 5 minutes on the road at highway speed. Very strong acceleration from a stop to 80 MPH, no missing.
My Genisys misfire counter shows the #1 and #4 cylinders are acting up the most.
The shop before me installed:
Cap, rotor, wires, coil, AC Delco Plugs, crank sensor.
After double checking their work, I installed a replacement spider, (happened to have an extra) with new regulator, no change.
I pulled the distributor, found the gear worn, replaced. Did the cam/crank sync procedure. No change.
Friday I replaced the ECM with a Napa Reman, flashed it in house, no change except the new torque convertor circuit problem, reinstalled the old ecm, verified the TC circuit problem was gone, and shipped back the defective "new one" .
Map, Maf, Tps, Cts sensors all look normal. Cam and Crank sensors look good on the Vantage. I blocked the EGR off to make sure no leak there.
On startup, the CMP shows 0 on the scanner, after revving engine, defaults to -12 or -13.
Fuel pressure KOEO 60 psi. Running down the road, 54-62 psi.
Anybody have any ideas? Thanks, Joe

Welcome to AF. The cam synch can only be set after the engine is revved above 1k then it should be reset then rechecked in the same manner, was this done?

I have done the sync procedure multiple times with my Genysis scanner. It syncs normally. When I start the truck, before any acceleration, the CMP Retard shows 0. After revving the engine one time, it goes to negative 13. I let it run for appx. 15 minutes this morning at idle while watching the cam and crank sensors simultaneously on my Fluke 98. They have perfect signals, right in sync with each other. The truck was running rougher than normal at this time, and i noticed the cam retard was at negative 28. I am considering advancing the distributor one tooth, and re - sync - ing again. Maybe timing chain slack?
Thanks, Joe

Even a slack chain should allow you to get it closer than 28 degrees.

You might pull the distributor and check the gear. We've gotten two or three this year from a local vendor that the !%@% gear spun on. It's not something you generally think about, (especially if it's new) and can really foul up your day. Gluck!

I have done the sync procedure multiple times with my Genysis scanner. It syncs normally. When I start the truck, before any acceleration, the CMP Retard shows 0. After revving the engine one time, it goes to negative 13. I let it run for appx. 15 minutes this morning at idle while watching the cam and crank sensors simultaneously on my Fluke 98. They have perfect signals, right in sync with each other. The truck was running rougher than normal at this time, and i noticed the cam retard was at negative 28. I am considering advancing the distributor one tooth, and re - sync - ing again. Maybe timing chain slack?
Thanks, Joe

The cam shaft retard should not be changing unless the dist is moving or the gear is worn out or the rotor on top is moving off center.

Pull dist and check gear and rotor.
For setting the dist.
http://files.automotiveforums.com/gallery/showphoto.php?photo=51302

If the dist is off that much and you can not get it centered.
I have had some that removing the dist and turning the gear on dist shaft 180 degrees or a half turn will help center the up.