Misfire at higher rpms

[Supercharged111]

I don’t think I have a wide band as I don’t know what it is. I am willing to get stuff though. I just have no idea with this computer stuff. I know tbi is pretty basic it’s just not anything I have ever dealt with.

I suspected such, which makes it all the more heinous that you have someone tuning the thing with zero feedback. Your tune sucks, and that's likely the majority of the issue here.

 

[95er]

Is this a "liquid filled" pressure gauge? Do you burp the gauge before taking a reading


Knock counts. Knock sensor activity.

 

[95er]

It is a liquid filled gauge. I have never heard of burping the gauge before.

 

[PlayingWithTBI]

That's what the spring--in combination with the adjustment--does.

^^^This. To expound further - the higher the pressure, the more fuel you get. As an example, 16 PSI will give you ~67.7 Lb/HR each (supports 256HP @85% Injctor Duty Cycle at 0.45 Brake Specific Fuel Consumption). 18 PSI will give you 71.8 Lb/HR (supports 271 HP). 20 PSI will give you 75.7 Lb/Hr (supports 286HP). Source - DynamicEFI. com "EBL Utility". You get the point...

The last time I read Harris' blurb about "Recommended 350 TBI Mods" he also suggested an AFPR (Adjustable Fuel Pressure Regulator) about 5 years ago. I got one set up from RV Morse Machine but he passed somewhere ~3 or 4 years ago.

Here's a website that stocks this stuff. You'll want a 30# gauge (not liquid filled) and maybe a 90° street El for it.
www.marine-performance-parts.com/gmtbiperformance.aspx

CFM Technologies

CFM Technologies sells and manufacturers Magazine + TV Featured performance parts for GM TBI , Throttle Body Injection, along with custom carburetor spacers and the famous HVH Super Sucker Carb Spacers.

marine-performance-parts.com

 

[95er]

So I just ordered the gym tbi tuner starter kit from boostednw. I am not sure if I will do my own tuning or not since I really don’t know what I am doing but for the price it made sense to get the whole kit and just start of at least with data logging. I am just unsure what to do with the data once I get it. Next on my list is the new fuel gauge and adjustable spring. I am hoping though I can make this all work with what I have currently. Thank you everyone for the advice and please keep it coming.

 

[Scooterwrench]

Once you learn to read the data it will tell you what your engine is doing. You will have to buy more hardware to change any of the tuning. Boosted NW also sells an emulator that allows you tune on the fly but you will still have to buy a burner and chips to burn the most favorable tune onto a chip.
The emulator only allows your PC to become a temporary chip that you can change the settings on while it's plugged in.

 

[Schurkey]

It is a liquid filled gauge. I have never heard of burping the gauge before.

Liquid-filled gauges ALWAYS have a rubber plug in them somewhere, that plug has to be mounted "up" when the gauge is installed. The plug has to be burped before each use if the gauge experiences temperature changes...like going from ambient temp to engine-compartment temp.

As the temperature increases, pressure inside the gauge causes a reduction in indicated pressure. Speaking for fuel pressure gauges specifically, the indicated pressure goes lower and lower as the gauge gets hotter and hotter.

Then you burp the gauge and get accurate readings again. When the gauge cools off, you get the opposite effect. So it has to be burped again to restore proper internal pressure.

Many of the rubber plugs have a little nipple that can be sliced, to provide a full-time vent. But in a car, the silicone fluid sloshes from G-force, and spills out the vent hole.

 

[95er]

So since most people think it’s a fuel issue this brings up another question. Since my intake is a carb intake with a tbi adapter on it, when I place the adapter, part of the intake protrudes into one of the circles for the tbi fuel port. If I ported this part to make it completely round and open could it fix my issue? I know it would be a good idea and could make things work better and should do in the future no matter what but could it be the cause of this or are we pretty sure if everything else is working right that it’s a tuning issue?

 

[Scooterwrench]

So since most people think it’s a fuel issue this brings up another question. Since my intake is a carb intake with a tbi adapter on it, when I place the adapter, part of the intake protrudes into one of the circles for the tbi fuel port. If I ported this part to make it completely round and open could it fix my issue? I know it would be a good idea and could make things work better and should do in the future no matter what but could it be the cause of this or are we pretty sure if everything else is working right that it’s a tuning issue?

Port matching is one of the best things you can do to make power but unless there is an interference issue with the throttle plates I don't see that as the problem. You more than likely have a tuning issue. I'm thinking he was trying to fix you up with lean cruise and didn't add in enough PE(electronic version of power valve)and/or AE(accelerator pump shot)or he just has you running too lean overall.
Before you can blame the tune you have to find out what your fuel pressure is at WOT under load.

 

[95er]

Ok so I hooked my fuel pressure gauge up with the release valve and the cheap tubing. The gauge read 20psi. When I pressed the relief button it dropped to 10 psi. Which according to a response to me should be remain at around the 20 psi. So if I am understanding everyone right is a fuel pump issue. If this is the case what does everyone recommend for a fuel pump. Is there anything else I should be looking at? The filter is a brand new k&n filter along with the fuel pump being the Delphi pump for the 96+ k1500 which is supposed to handle higher pressure. Thanks again everyone for the advice.