99 5.7 shuddering/low power, no codes

[L31MaxExpress]

Thanks for all the help I’ll try it out soon

Adjust those and if the engine is running on 10% Ethanol fuel which is at almost every pump now days, set your Stoich Air/Fuel value to 14.1. If the engine is stock, that should make the fueling much more accurate with the GM VE table and MAF curve in place.

 

[JoshCampbell55]

I get those same blips when I snap the throttle a bit and let off. I have noticed those on pretty much any engine and never felt it was something to worry about.

So I drove the truck for about 18 minutes and didn’t get a single misfire while driving and it doesn’t seem to be studdering anymore. I recorded a short video on what I’m talking about when you rev it at idle and it gets a few misfires. it does seem to vibrate at idle but I haven’t driven one of these trucks in so long that I can’t remember how smooth they are supposed to be

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[L31MaxExpress]

So I drove the truck for about 18 minutes and didn’t get a single misfire while driving and it doesn’t seem to be studdering anymore. I recorded a short video on what I’m talking about when you rev it at idle and it gets a few misfires. it does seem to vibrate at idle but I haven’t driven one of these trucks in so long that I can’t remember how smooth they are supposed to be

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Mine always had a bit of a rough idle too it. When I say rough idle, it had some barely perceptible shuddering/roughness to it at idle caused by the PCM manipulating the timing advance up to 20° to control idle speed. When you look at the advance at idle it will be like, 23, 18, 28, 15, 30, 23, 17, 24, 22, 19, etc, etc. Since the timing is always boucing around the engine never runs completely smooth like say a stock 350 carbureted engine.

 

[JoshCampbell55]

Mine always had a bit of a rough idle too it. When I say rough idle, it had some barely perceptible shuddering/roughness to it at idle caused by the PCM manipulating the timing advance up to 20° to control idle speed. When you look at the advance at idle it will be like, 23, 18, 28, 15, 30, 23, 17, 24, 22, 19, etc, etc. Since the timing is always boucing around the engine never runs completely smooth like say a stock 350 carbureted engine.

Yea mine does that too. Thanks for all your help man I think I’m going to try to change the ECU stuff and then just call it good