My 454 Rebuild

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Spareparts

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Comp is 155 to 160 all cylinders. Leak down was done and I don't remember readings but was good.
 

ralmo94

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How bad is the misfire, is it at all rpm or just idle? Black boxes have misfire code disabled from the factory for the l29.
 

BeXtreme

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I think he means the individual cylinder location misfire codes are disabled in the black box? I think the older black box ECM's didn't have the crank location resolution to be able to tell the individual cylinder that was misfiring.. maybe?
 

454cid

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I think he means the individual cylinder location misfire codes are disabled in the black box? I think the older black box ECM's didn't have the crank location resolution to be able to tell the individual cylinder that was misfiring.. maybe?

Oh, meaning they all show up as Random Multiple Misfire? P0300, I think?
 

Spareparts

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It is a 0411 ecu. It will show misfires on individual cylinders but will not show a cel for it.
The only thing I have that will show it is Dash Command
 

Mangonesailor

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I think he means the individual cylinder location misfire codes are disabled in the black box? I think the older black box ECM's didn't have the crank location resolution to be able to tell the individual cylinder that was misfiring.. maybe?

Oh, meaning they all show up as Random Multiple Misfire? P0300, I think?

I think the Black boxes just simply don't have the computing speed to pick up slight misses that a bad dizzy gear and other tiny issues give you, but they'll pick up a dropped cylinder for-sure.

I had a P0300 the day after installing my 0411 and getting the crank relearn done. The history on the suspect cylinders would hit in the hundreds while the engine was warming, but you couldn't even feel it miss. Off-idle though or revved up, no misfires. I swapped the dizzy (because of a knife-edged dizzy gear) and the "misfires" went away. Didn't have that going on just days before when I had the black box installed.

@Spareparts have you tried gapping #4 and #7 to .045" yet to see if that makes any difference? I know you said you gapped to .050" before.
 
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Spareparts

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Something is odd. I tried logging date on the way home from work.
With the 0411 i'm not seeing the cylinder misfire data like i was before. Maybe i was seeing it with the black box? I put the 0411 back in 2 weeks ago i think, and now im pretty sure i was seeing it with the black box.
Here is a big clue i think.
When cold my CMP is + - 0.3, Never checked it hot that i remember. Today when driving home i was watching it. Cold it started at + - 0.3 as usual but once it was warm
it was varying from +1 to +3.5. That's dam odd for sure. Keep in mind it has a new melanized gear when installed with the new engine and acted the same sense first start. Timing chain/gears were new and tight like a new one should be.
This type of data is what leads me to replace parts that are not acting right but before i do that again what do you think?
 

ralmo94

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This makes no sense to me. Where did you learn this?
Go to the HP tuners repository and download any stock l29 files. All the ones I've looked at have misfire disabled. Seen it was disabled on my truck and I thought maybe someone had been in the tune before, so I began to look and see what if anything was different than a stock tune. Mine was in fact stock, or at least everything was exactly the same as all the other l29 stock bins I looked at.

Point is, if they have that disabled stock, how smooth can you expect to get it?

Min has a little sort of hiccup type misfire at idle, seems to be resolved somewhat by raising the idle. At least not as bad at 700 rpm as it is at 600.
 
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