bad or going bad injectors?? im a noob.

[DAVe3283]

A LB7 with stock injectors is extremely tough. Obviously not indestructible (as evidenced by the previous engine), but I doubt you've done anything to it with a little fuel knock.

Since this has been happening the entire time with the replacement motor, I would personally start with swapping in a stock tune. Either have a dealer reflash the current ECU, or grab a used ECU from a junkyard/eBay and have that flashed to stock.

Once you have a stock tune, see how it runs, and we can start diagnosing properly. It is hard to say what values are normal when an ECU is tuned, since we can't know what the tuner did to various parameters.

If the replacement motor had original injectors in it, they are now at 120k miles, and are quite likely failing at this point. But it would be a very expensive experiment to just replace them and see if that fixes the fuel knock.

 

[David_1025]

A LB7 with stock injectors is extremely tough. Obviously not indestructible (as evidenced by the previous engine), but I doubt you've done anything to it with a little fuel knock.

Since this has been happening the entire time with the replacement motor, I would personally start with swapping in a stock tune. Either have a dealer reflash the current ECU, or grab a used ECU from a junkyard/eBay and have that flashed to stock.

Once you have a stock tune, see how it runs, and we can start diagnosing properly. It is hard to say what values are normal when an ECU is tuned, since we can't know what the tuner did to various parameters.

If the replacement motor had original injectors in it, they are now at 120k miles, and are quite likely failing at this point. But it would be a very expensive experiment to just replace them and see if that fixes the fuel knock.

that was my thinking on trying to grab another ecm. i will try to accommodate this as quickly as possible. when searching for a new one is there anything " red flags" that i need to look out for i.e. from a junk yard ect. besides the obvious no tunes..lol

 

[DAVe3283]

It is hard to tell in advance if a junkyard ECU is locked. If you can get photos of the truck it is coming out of, that can often give you clues the truck was tuned or not. I have had good luck so far with all the ECUs I have bought being unlocked.

 

[2004LB7]

MAF at 44 looks good.

You very well might have a handful of leaking injectors. If the balance rates drop to 0 that means the conditions are outside the parameters required for the ECM to run balancing on the injectors - MPH, throttle, too much balance, and possibly others

If you get another ECM, especially from a junkyard, it will need to be programmed as the VIN will need to be updated. If you are going to do that then you don't need to worry about it being locked. The dealership or anyone with the tech 2, EfiLive, etc can program it.

 

[David_1025]

It is hard to tell in advance if a junkyard ECU is locked. If you can get photos of the truck it is coming out of, that can often give you clues the truck was tuned or not. I have had good luck so far with all the ECUs I have bought being unlocked.

ok. thank you very much for your time and advice. i will try to get my hands on a new ecm within the next week.. i live somewhat close to a huge duramax bone yard in hicksville ohio. they usually have alot of these in stock .

 

[David_1025]

MAF at 44 looks good.

You very well might have a handful of leaking injectors. If the balance rates drop to 0 that means the conditions are outside the parameters required for the ECM to run balancing on the injectors - MPH, throttle, too much balance, and possibly others

If you get another ECM, especially from a junkyard, it will need to be programmed as the VIN will need to be updated. If you are going to do that then you don't need to worry about it being locked. The dealership or anyone with the tech 2, EfiLive, etc can program it.

i can get my hands on a tech 2 from a friend of mine, is is difficult to reflash the unit myself or shoul i let someone who knows what they are doing go after it?

 

[1FastBrick]

A tech 2 alone won't be able to reprogram the ECU. You need to purchase a subscription through AC Delco in order to obtain the stock file and be able to flash it.

It's not difficult, however it's not a breeze either if you have never done it. Especially if they don't have the calibration for your vin. You have to call there tech support and they have to add it from the old system to the new system.

 

[David_1025]

A tech 2 alone won't be able to reprogram the ECU. You need to purchase a subscription through AC Delco in order to obtain the stock file and be able to flash it.

It's not difficult, however it's not a breeze either if you have never done it. Especially if they don't have the calibration for your vin. You have to call there tech support and they have to add it from the old system to the new system.

got ya . he is a gm dealer mechanic maybe he has the subscription , im not 100% sure.. thanks for the feedback.

 

[David_1025]

update on MAF replacement.. after a 20 min drive balance rates became alive at idle .. new MAF hanging around 44-45 ish, main fuel came back up to 5mm cubed, and balance rates have returned.. will log new readings shortly. again, thank you everyone for the help