My 454 Rebuild

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ralmo94

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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?
I thought CMP was supposed to be set at operating temp?
 

Spareparts

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I thought CMP was supposed to be set at operating temp?
I dunno, i never read that and you're the first to mention it.
If that's true about the 0411 i will put the black box back in. I have 0 experience tuning and i don't need the added headache of a swapped ecu not quite right especially when trouble shooting.
 

ralmo94

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I dunno, i never read that and you're the first to mention it.
If that's true about the 0411 i will put the black box back in. I have 0 experience tuning and i don't need the added headache of a swapped ecu not quite right especially when trouble shooting.
How bad is the misfire? If it's not that bad, it could just be the nature of the beast.
 

Spareparts

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It's almost like a dead cylinder when cold but doing a drop test they all have the same effect.
Hot its almost gone and doing a drop test they all have the same effect with none giving a definitive answer the same as cold.
 

ralmo94

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Have you tried reading the exhaust temp of each cylinder with an infrared thermometer?

Also, as someone else suggested, are you 100% sure you didn't possibly get any wires mixed up with a repin?

Maybe check with a timing light on each cylinder to verify it's ignition related?
 

termite

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I thought CMP was supposed to be set at operating temp?
I seem to remember hearing that about setting it on the 99 5.7 i used to drive after doing intake gaskets. I never fooled with it. Just kept tweaking dizzy till CEL stayed off (bulb did still work).

I'm hoping you get it sorted out here shortly before drastic measures happen :weld:.
 

L31MaxExpress

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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.

Idle Misfire was off in the OEM GM 2005 L31 350 calibration I run my pig on. My 97 has had what I would consider a rough idle since 1998 when it had 13K miles on it.
 

L31MaxExpress

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Part of me is almost thinking he needs to go into the scanner tool on HP Tuners. Go into the vehicle controls. Disable Fuel Trims, Clear Long Term Trims, then Disable Idle Spark Variation. The PCMs manipulation of the fueling as well as the idle timing to control idle rpm as well as keeping the catalytic converter happy with 02 cross counts causes rough running compared to what a well-tuned non-feedback system would reach at equilibrium.
 

ralmo94

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Part of me is almost thinking he needs to go into the scanner tool on HP Tuners. Go into the vehicle controls. Disable Fuel Trims, Clear Long Term Trims, then Disable Idle Spark Variation. The PCMs manipulation of the fueling as well as the idle timing to control idle rpm as well as keeping the catalytic converter happy with 02 cross counts causes rough running compared to what a well-tuned non-feedback system would reach at equilibrium.
If he doesn't have HP, he could unplug O2's that would force open loop, fuel trims would need battery unhook, but constant timing, don't think you can get it without scanner command or a reflash.
 
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