Well, I've been putting some miles on the new 370 engine. The first thing I noticed was the supper supper shitty gas milage. I was getting 12 in town. Then there was the lack of power. it felt like my old wounded 5.3 at 135 kpa. Needless to say I was too happy until I turned up the boost. Then more issues. a strange misfire would come in at any given rpm once the map cleared 150ish kpa. switch back to low boost, all was good up to 6,000 rpm. And on top of all that, the engine seamed to have a engine misfire at times....

More info about the truck....
LQ4 .030 over
10.1 wiseco pistons
44 injectors (3 years old)
stock y2k coils/wires
tr6 @ .035
dwell at 5.7-5-9msec in high rpm/load

I also should say the old 5.3 was getting pretty bad gas mileage near the end of its life as well.

The first order was to track down my misfire. I pulled plugs, scoped each cylinder, moved injectors/coils and plugs around. What I found was number 6 seamed to run a bit richer than the rest. Funny, the old 5.3 had a dead number 6 at times too.....

bad bore-a-scope shot of number 6

I moved the number 6 injector to number 1, and replaced the number 6 plug. a few weeks later I pulled the plugs again to find.....

Great, problem solved!!! It was the.......spark plug?????
Whatever

I drive it for a few more weeks, no more engine misfire at idle, but still low on power and missing in high boost. Finally think to try new coil packs and wires. Problem solved, no more high end misfire, BUT a **** TON of kr, all the time... make me think I screwed up and built a 13:1 compression engine.
I try more fuel, less timing, nothing is getting rid of my kr. I could command 11:1 a/f and 0 deg advance and I would get AUDIBLE detonation at 110kpa. I figure it Must be injectors, maybe one is not spraying well causing a lean cylinder. ????????

I run open loop and a flat 10 deg advance and 12.5 a/f ALL the time. I put 70 miles on the engine, (last week) pull the plugs thinking they will tell me which injector is causing the problems. The result? 3,4,5,6 look lean, 1,2,7,8 look leaner

As I'm reinstalling the plugs a thought occurred to me.. What if g.m changed some of the dwell settings with the newer round style coil packs? I check and found one table very slightly different. While I was there I thought I would try the stock dwell settings too. filled the tank with fresh fuel. NO MORE KR.... It's only been two days, but GOD willing the end of my problems.........
Thank you, That is all

 

What? Its fixed?

 

aaaah, I think so.... Did a few high boost runs, but tuning is still way out (sub 10:1) so today I stuck with low boost no kr at 10deg advance and a bit lean on the a/f as I dial in the v.e......

BTW, Thanks for all your help....

 

No problem. I am happy to hear some good news. When can we line them up?

 

aaa, after you reinstall a radix.....

I hope to be ready before the year is out, but with all the money I owe, I might not be able to swing a new windshield.. Which is now the only think keeping me from hitting the track other than tuning.... as long as the truck decides to keep working that is...

btw, I started playing with transient fueling FINALLY, kicks ***.... I'll give ya a call in the morning...

 

When I did the 6.0 swap, I just reused my 2000 4.8L coil packs. The LQ9 coils were a little dinged up so I just threw them away. Now I've learned that the LQ9 coil packs are stronger !!?? Would it benefit me to get another set of lq9's?

 

I can tell you from experience and monkeying with the dwell settings is that it's not worth it. No matter what I tried on my truck for dwell settings is it would cause a lot of audible knock and performance was down. As a matter of fact, increasing the dwell heated up the coils more than I liked too. They were so hot that you'd burn yourself if you touched them after driving around for 20 minutes. When tuning or helping someone with tuning I recommend never touching the dwell settings for the coils. It's not worth it. I think you found your problem as this sounds like it would be caused by too much dwell.

 

I could agree, but the thing that bothers me is, I turned up the dwell a LONG time ago, and at the time it seamed to help. maybe the coils were already getting tiered...

 

So that's it then, no fueling issues? 44lbs injectors are enough to feed that monster? So happy that you solved the problem, I know how frustrated you were getting.

 

I remember reading about dwell issues awhile back. I remember Parish saying it caused him probems once he started messing with it. I have also seen a bunch of posts on HPT about not messing with it. I hope that was the problem, I guess your coils didnt like to play well with those dwell settings.