My 454 Rebuild

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Spareparts

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My old engine idled perfect once i put new 5o injectors in it hot or cold. They were switched to the rebuilt engine.
Feeling like a dead cylinder when cold and a slight misfire when hot driving is not normal.
Yes i have tried a temp gun but i can't get any reliable reading to compare cylinders from the manifolds.
I have measured the temp sensor on the front and its pretty dang close to what Dash Command says and what the ecu should be seeing.
 

Spareparts

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I have tried it with the MAF unhooked and it was better. Only for about 10 miles and was still not good but better.
Also don't have HP tuners
 

BNielsen

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We should probably link this thread to the Vortec 454 thread for future trouble shooting.

I feel like you're right on top of getting it ironed out; definitely making me hyper aware of things I should be on the lookout for once I get started building a new mill for my truck.
 

Mangonesailor

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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.
I used to have that. I sat in my driveway for about an hour forcing the IACV to different RPMs that ran the smoothest, then I adjusted spark advance for maximum vaccuum. Then RPM again, then timing. I adjusted my tables to match that. I also played with the commanded AFR when in open loop at low temps. Engine idles a helluvah lot smoother than it did before I did all that.

It's worth the effort.
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.

I would most-definitely move the dizzy then a little retarded and try to get your hot offset to be +/- across 0*, just to be absolutely sure (or do it after you install a new unit, should you do that). You don't have the ability to re-learn the crank offset though do you, you have to go to a shop. Right?

As far as logging your misfires, did you tell dash command that you're now in a 01 chevy van and all that so it sought out the correct PID addresses? You may be telling it that you're still in a '98, so it's telling the ECU it wants shrimp cocktail and the ECU is blowing a kazoo.

Just having PCM scanner software from HP tuners would make this all WAAYYYYY easier.. Even a datalog from dash command.

Also, are you going to try my suggestion with the plug gap on those two cylinders? I think the timing light on each cylinder would be a good idea, just to see it.

@BNielsen , I think whenever he finds the solution he should post something in that thread. This thread is already 50 pages long, we've got a lot of people posting, and I'm sure I'm not the only one having a hard time keeping up with what he's done, checked, noticed, and what people have already suggested.
 

Spareparts

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I set Dash Command to a 2002 chevy Express van. I'll see what it says in the morning.
 

ralmo94

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My old engine idled perfect once i put new 5o injectors in it hot or cold
Am I understanding correctly, that you are using the same 5.0 stock replacement bosch injectors that you used when idled smooth previously?
 

Spareparts

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I was. Right now i have reman stock style injectors in it. Switching changed nothing.
This weekend i will likely put them back in. I have a injector tester coming that will be here tomorrow.
Plan this weekend is to take the intake off. Test every injector i have 24 stock style 8 are reman and 8, 5.O injectors. The 5.O injectors are less than a year old. I will have 8 good injectors either 5.O or stock that flow the same and don't bleed off. I don't think i have had a injector problem anyway.
Change distributor and adjust CMP when hot!
 

L31MaxExpress

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I was. Right now i have reman stock style injectors in it. Switching changed nothing.
This weekend i will likely put them back in. I have a injector tester coming that will be here tomorrow.
Plan this weekend is to take the intake off. Test every injector i have 24 stock style 8 are reman and 8, 5.O injectors. The 5.O injectors are less than a year old. I will have 8 good injectors either 5.O or stock that flow the same and don't bleed off. I don't think i have had a injector problem anyway.
Change distributor and adjust CMP when hot!
Hot or cold does not seem to matter, atleast with my old 350 and current 383 in the van and the other 305s and 350s I have adjusted. I look at what it is on a throttle blip. It will bounce around a bit if the engine is not accelerating, pulling the slack out of the timing chain and the distributor drive gear. I actually find the readings more stable with cold oil because the pump and thus drive gear and timing chain are under more load. It will always retard a bit as the rpm increases.
 
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