99 5.7 shuddering/low power, no codes

[L31MaxExpress]

A new fuel filter never hurts. Your pressure might be a bit low, I think these Vortecs call for 60-66 KOEO and tend to drop into the 50s while running. Generally a failed regulator causes the pressure to bleed off after shutdown in my experience, so at least your new injector units regulator seems OK. New filter should bring your pressure up a bit, so retest with the new filter on and see what you get.

Other than intake gasket, and assuming your new injectors aren't a factory defect part, I'd take a look at the distributor itself. If it's an original plastic-body unit they like to crack which can throw things off.

Also recommend taking a look at your idle air control valve. If that gets sticky or fails it'll starve the engine for air when the throttle plate is closed (like when coasting, or at full idle) and can cause rough running in those conditions.

MFI update spider is ~58 psi KOEO and drops at idle.

EDIT- I still do not get how GM gets away selling that updated spider without reprogramming the PCM with the correct injector data. What is in the PCM for the stock spider is wrong for the updated spider. I put the newer injector data in mine years ago and it ran much better all around.

 

[L31MaxExpress]

Also in an extreme case, 700r4 with crossflow the engine would stall with the shifter moved to Reverse or Drive. The torque converter clutch was applying as soon as the transmission pump built pressure.

 

[JoshCampbell55]

Alright I fixed the vacuum leak in the intake tube to throttle body. No change. the truck has been sitting for a few days and it seems like when I start it after it’s been sitting the RPM’s drop low for a second before it levels out. I’ll check the fuel pump voltage this weekend

 

[JoshCampbell55]

New fuel filter and then cleaned the ground for the pump. No change. it’s hot today so tomorrow morning I will try to check the voltage to the pump.
heres a video of the fuel pressure

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[JoshCampbell55]

Checked under the intake manifold to see if there was any leaks. There is some wet spots but I can’t tell if It just came from the fuel lines when I disconnected them

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[JoshCampbell55]

MFI update spider is ~58 psi KOEO and drops at idle.

EDIT- I still do not get how GM gets away selling that updated spider without reprogramming the PCM with the correct injector data. What is in the PCM for the stock spider is wrong for the updated spider. I put the newer injector data in mine years ago and it ran much better all around.

Where did you get this data from? My ecu is unlocked with HP tuners so I have the capability of changing things

 

[JoshCampbell55]

So I’ll add that on the log the only time I’m getting misfires is when letting off the throttle, seems to be cylinders 1-4 mostly. If I blip the throttle once I let off I’ll get around 6-10 misfires total on those cylinders until it reaches idle again

 

[L31MaxExpress]

So I’ll add that on the log the only time I’m getting misfires is when letting off the throttle, seems to be cylinders 1-4 mostly. If I blip the throttle once I let off I’ll get around 6-10 misfires total on those cylinders until it reaches idle again

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.

 

[L31MaxExpress]

Where did you get this data from? My ecu is unlocked with HP tuners so I have the capability of changing things

I pulled them out of a 2010 Express 4.3L that uses those injectors from GM. That system uses fixed fuel pressure, but you only need the data from the 400 kpa row that coincides with 58 psi.

At 58 PSI the flow rate is 21.3 lb/hr.

Minimum Pulse Width 0.797 msec

Fuel Rate Modifier vs Battery voltage
5v---0.981
6v---0.981
7v---0.981
8v---0.981
9v---0.981
10v--0.981
11v--0.981
12v--0.985
13v--0.989
14v--0.993
15v--0.998
16v--1.002
17v--1.006
18v--1.011

Offset vs Volts vs MAP
4---0
5---13.9531
6---13.9531
7---11.0781
8---3.7734
9---0.09766
10--0.7578
11--0.6328
12--0.5078
13--0.4297
14--0.3594
15--0.3125
16--0.2500
17--0.2188
18--0.1719

On the 0411 and P59 stuff I have seen the stock tables are in 1/2-volt increments where the E37 was in 1-volt increments. Fill in the known values, then interpolate between those known values. Since the differential pressure across the injector is the same throughout with the vacuum referenced regulator, the values copy straight across the whole tables.

Finally last but not least, the short pulse adder limit is 4.0msec. Make sure to note that the units in parenthesis are negative.
Short Pulse Adder vs PW
0.000-----0.000
0.125-----0.0391
0.250-----0.0391
0.375-----0.0469
0.500-----0.0469
0.625-----0.0469
0.750-----0.0391
0.875-----0.0156
1.000-----0.0078
1.125-----0.0000
1.250----(-0.0156)
1.375----(-0.0313)
1.500----(-0.0469)
1.625----(-0.0391)
1.750----(-0.0313)
1.875----(-0.0313)
2.000----(-0.0234)
2.125----(-0.0156)
2.250----(-0.0156)
2.375----(-0.0078)
2.500-----0.0000
2.625-----0.0000
2.750-----0.0000
2.875----(-0.0078)
3.000----(-0.0078)
3.125----(-0.0078)
3.250----(-0.0078)
3.375----(-0.0156)
3.500----(-0.0156)
3.625----(-0.0156)
3.750----(-0.0156)
3.875----(-0.0156)
4.000----(-0.0078)

 

[JoshCampbell55]

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