I've noticed recently that my mileage is a bit worse than usual (even for a LLY), the EGTs seem a touch higher than previously (but that could be due to it being 91* out), and the idle feels a bit rough... I did a scan of the injector balance rates, and they aren't too even, but I have no idea how to interpret the scan. It's not in %, it's in inches. Below is the graph of the scan. The top frame is cyl 1-4, middle is 5-8, and bottom is Engine RPM. Any of you guys know how to interpret it? Thanks.

http://picam.modularmn12.us:81/images/truck/balance.jpg

A week and 35 views and nobody has a clue?

A couple of comments:

1. Balance Rates are only calculated at idle. The purpose of this engine function is to smooth out the idle. Nothing more. Once you increase engine RPM above idle, the balance rates go to a default value (something like 0.82 mm3 - I can check later for you if you want). You can see that on your plots, as engine RPM goes off idle and balance rates flat line. Engine at idle, they are fluctuating. So this makes sense.

2) Not sure what you are measuring the data with, but your units a messed up. I am going from memory here, but I think the readout on my Predator (and as listed in the service manual) is in mm3 of fuel. The dimension/unit is a volume. The balance rate is an addition or subtraction of a very small amount of fuel from a standard default injection amount at idle. As I wrote previously, the only intend is to balance the amount of torque each cyclinder produces at combustion, thus smoothing the idle. You need to fix your units before you proceed. "Inches" are not correct. The units are a "volume" and metric. You should also see some "plus" and "minus" signs.

Hope this helps,
Alan

I know the readings are screwey.. I use Ease Simulations GM Enhanced PC Based Scan tool. I've spoken to them, and they are trying to get GM to give them the proper information for te new V4.1 scan tool.

The two options are inches, or mm. If I set it to mm, it reads something like 4600.0. HOPEFULLY Ease will get information from GM and have it read like a Tech2 so we can actually understand it.