It is like something is putting a load on the engine. In the mornings, I can see my headlights intensity change with the fluctuations. I do not have the EGR pluggged in still. My valve was bad so I put a block off plate in its place. I do not notice any change in my boost readings when this happens.
This on-off cycle of the compressor, how quickly does this happen?
If I plugged the EGR valve in, the connector, but not the valve to intake, would this help. The only reason I say this is because I know the valve is weak and don't want to run into other issues. I will try it to see if it does anything and reply back. It can't hurt.
Does the normal idle cycle program happen everytime you come to a stop? Does this cycle begin at a certain rpm, like when at idle or stopped (in gear)?
With certain year trucks and certain PCM stadegies there are side effects with unplugging the egr valve. Some of the side effects are, VGT won't cycle, Clutch fan won't reach full RPM speed, and CEL will come on.
The A/C compressor will cycle on/off with just the heat turned on, this allows the R-134 freon to keep the seals conditioned for the A/C system. When you start the truck, with the heater controls turned off, open the hood and the a/c compressor should not be spinning. Now with the truck still running, turn on your heat and take a look at the A/C compressor, it should be cycling on/off. When the heat is turned on at first the compressor should run about 1 minute, after that it will turn off and cycle evey 10 seconds. This is perfectly normal. You need to take notice when the compressor turns on if your lights are dimming. The dimming lights may be a loose ground cable, look at and try to move your battery cables for a loose connection. Also crawl under the truck on the pass side at the bottom front of motor and look for the main battery ground cable, see if it's loose or a coroded connection.
The VGT cycle is controlled by the PCM, I'm not sure how or when the PCM decides to cycle the vanes, but it should cycle whether your in park or in gear at a stop light, This is not a constant program, it will only cycle in certain conditions. I believe the real early stradegies didn't have this VGT cycle program.
Let us know if you notice any difference after you plug in the egr valve, you can just plug it in and tie up the valve to the side somewhere without bolting it back into the manifold.
If the lights are only dimming in the morning when you first start it up, it's the glow plugs that are turning on for about 1 minute, after that they step down in power. You can pick up a cheap voltmeter from walmart or a parts store that plugs into the cigarette lighter to check your volt output. Before start up the volts should be 12v-13v, then after start up they should be around 11.5v while the glow plugs are on for about a minute. When the glow plugs turn off the volts should jump up to around 13v-13.8v
Another way to test is to but a clamp on DC amp meter and check the amps from the red wire coming off the alternator. The amps at start up should be around 80amps, then slowly drop as it idles, to around 40amp.
It's possible that the the alternator took a dump. Even though you replaced both batteries 6 months ago, your first alternator that failed may have weakened or damaged them. A weak charging system on the 6.0 can result in damaging the FICM. And that could lead to failed injectors.