I realize now my question wasn't specific enough. What I was asking about "all in" was if you had a 4.3 like me in an 01 if you had a specific total advance in mind? I fully understand the older models with their mechanical, initial, and vaccuum advance systems as I have worked on too many of them to try to count. My truck never pings no matter what I do or how I drive it. Yes, I had reflashing the pcm in mind and perhaps also adding a digital O2 sensor so the optimal air/fuel ratio can vary over a wider range in concert with the reflash.HenryJ wrote:You have little if any control over the timing on your truck. The PCM controls ignition timing.
"all in by 2500" refers to the point where all the available advance is achieved.
That is where the brain of our truck is an improvement. It can make adjustments on the fly.
What control do you have over this type system?
Not much. You can change fuels to help eliminate detonation and the resulting timing retard. You can reprogram the PCM by flashing the chip with a programmer.
What is the "right" thing to do? Maybe nothing. Do you have a problem? Is there another way to fix it without altering the timing?
Remember to keep it simple. The most complicated answer is not usually the best.
The problem? Less than acceptable performance and fuel economy.
Solutions tried thus far: new plugs, new filters (all of them also tried k&n air filter with no change), oil change and reduction in viscosity index from 10w30 to 5w30. new O2 sensors, blocking air injection pipes to verify no exces O2 leaking into exhaust throwing sensor readings to the rich side, new plug wires, new dist cap and rotor, egr limiter, verification tranny and overdrive and lockup operating properly, analyzer checkup of system to verify proper voltage outputs from coil etc and operation of all electrical systems analyzer can test, and cleaner run through fuel system to insure proper operation along with pressure and performance tests on fuel system. Cooling system temp consistent at 190-200 degrees except on pull in heavy mud then will go to 240-260 degrees. Transmission has large external auxillary cooler (17,500 gvw) and runs steady 190 degrees or less all conditions. Still has stock clutch fan on engine working okay.
To date the only thing which has made any significant difference was the replacement of the air check valves on the air pump system just ahead of the exhaust manifolds. This improved mileage from barely maximum of 14mpg to 16mpg. A far cry from the 20-21mpg I used to get. This mileage decline and noticable performance decline has occurred over the past 20k miles. The truck had 60k when I bought it and now has 83k. I also tried running premium regular with no noticeable improvement in performance and not enough improvement in mileage to pay for the difference in price. Tried gasohol too with too much loss in performance and mileage to be viable either. Even tried running tires all the way from 35psi up to 60psi with very little if any change in economy or performance. Brakes are near new and not dragging and emergency brake is new and also not dragging. No noticeable rolling resistance in excess of normal in neutral coast either. No topper or tonneau cover before or after just basic truck with nerf bars. Mileage and performance drop are primary concern and repair goal.
I know this is wordy but I wanted you to see I'm not just shooting in the dark or trying to outguess the system. I'm just struggling with what to do next. I also tried to be technically complete here so you might get a better idea or think of a better suggestion. I have previous professional dealership mechanic experience (16yrs) but no longer have my master-technician certification as I have been out of that business too long. Just more background and not bragging. Any suggestions you could make would be appreciated and seriously considered. Thanks
Not to belabor a question but can you tell me the difference between the early middle and late design 3.8 buicks other than the obvious plastic intake manifolds? 
HUGE improvement in driveability!!! Shifts went from better to INCREDIBLE!! 
Initial mileage check (20 miles unrepaired state balance of 250 mixture of interstate and short drives with some "gearheading" included. (trying out newfound performance) =17.46mpg. 
The higher the mpg's go the wider my smile gets. 
