Firing order

[welder350fd]

I have just finished rebuilding an '03 LQ4 with a com cams 54-424-11 cam, TBSS intake, 90mm TB, and ported 317 heads. The ECU I have is from a '99 2500 silverado 6.0 (NBS). i was looking at the tune on the '99 ecu and noticed the firing order is different than all the other 6.0 years ('02 for example). the order is correct, however it is jumped one position. See attached pics (left='99 right='02). is this a serious issue? thanks.

[mowton]

Funny you should bring that up, just had a long PM discussion with POWERZONE on the same subject. Even brought my buddy in who is a genius when it comes to late model and today's LS based engines and didn't really come up with a good explanation because actually its the same firing order.....So the last input from POWERZONE was info he got from another guy that said it was merely global reference point for the misfire/diagnostic system and has no effect on firing order.

So unless there is another reason which we would happy to hear, thats my story and I'm sticking to it :-)

Ed M

[welder350fd]

thanks for the quick response. Ok good to know, i guess if that did cause my timing to be off my 45 it wouldn't have started at all. in the process of doing some idle tuning, PITA. If it doesnt hurt I will make the firing order the way "it should be" just piece of mind. thanks.

[dermotw]

I don't have in depth experience of these ECU's (so perhaps I should shut up...) -but I do have some of other stuff, and I'd say you would be better off just leaving it as it is, because although I doubt it'll stop it running etc., it quite likely WILL mess up the misfire diagnostics, and perhaps some other diagnostics as well, if you change the order.
You may end up with either loads of false misfires reported, or none at all, ever, or even better, reporting CYL 5 when it's really 3 etc. No fun...

[welder350fd]

good point, I will leave it alone for now and see how it goes. I did get it running the other day so I am making some progress.