Tbi cuts off please help

[Marcus W]

I have a 1994 pickup 350 tbi with vortec heads, 650 cfm throttle body, 18 psi of fuel pressure, a chip, and other supporting mods. I’m having a problem where when I mash the throttle the truck will begin to accelerate and rpm’s climb and then all of a sudden it just dies. It doesn’t stall but I have to let off the gas for a moment and it will catch itself and I can continue on. My base timing is set at 2 degrees advanced but I wouldn’t think it would cause this issue, maybe though? My injectors and ignition system are in tip top shape so I’m really not sure. Is my computer going bad?

 

[PlayingWithTBI]

I have a 1994 pickup 350 tbi with vortec heads, 650 cfm throttle body, 18 psi of fuel pressure, a chip, and other supporting mods. I’m having a problem where when I mash the throttle the truck will begin to accelerate and rpm’s climb and then all of a sudden it just dies.

Who supplied the chip? Can you data log with TunerPro RT to see what's going on? If everything is good, I'd go back to your chip supplier.

 

[Marcus W]

Who supplied the chip? Can you data log with TunerPro RT to see what's going on? If everything is good, I'd go back to your chip supplier.

Tbichips made my chips, I have to buy a computer soon for school so I could start logging data and send it to them.

 

[PlayingWithTBI]

Tbichips made my chips,

Gee, why am I not surprised, ha ha.

I have to buy a computer soon for school so I could start logging data and send it to them.

Good plan!

 

[Marcus W]

Gee, why am I not surprised, ha ha.

Good plan!

Is there anyone else who burns chips for these trucks still?

 

[PlayingWithTBI]

Is there anyone else who burns chips for these trucks still?

Yep, there's folks on www.gearhead-EFI.com that do. Dave w (Old School EFI) for one. He'll have you data log, tune, data log, rinse and repeat.

Let's ensure your sensors, ignition, and fuel delivery are all good 1st. No amount of tuning will mask an inherent mechanical issue.

Let me guess, you read Brian Harris' recommended 350 TBI mods and built yours accordingly? Don't get me wrong, he had some good input but there are other ways, and maybe better, options. So, what cam, fuel pump, distributor, and IAC do you have? Did you go with quality parts or buy cheap replacements?

Do you have a fuel pressure gauge or are you going by the "advertised" 18 LB spring (probably from SPR Performance when you bought the 46mm TB from them)? Can you check fuel pressure while under load? A WBO2 is IMHO crucial for tuning "performance" systems.

Why do you have your base timing set at 2° when TBIchips should have set SA tables in his calibration? BTW, FWIU Harris retired a couple years ago, due to health issues, and someone else is running TBIchips.com

As I said, data logging is a great plan

Don't get me wrong, I've been there, done that, never could get mine running right until I explored other avenues. At least you hopefully have the faster (8192 baud as apposed to 160) '7427 which has expanded tables for better performance. My 7747 just couldn't keep up.

At least it was a helluvan education for me, still learning every day

HTH

 

[Marcus W]

Yep, there's folks on www.gearhead-EFI.com that do. Dave w (Old School EFI) for one. He'll have you data log, tune, data log, rinse and repeat.

Let's ensure your sensors, ignition, and fuel delivery are all good 1st. No amount of tuning will mask an inherent mechanical issue.

Let me guess, you read Brian Harris' recommended 350 TBI mods and built yours accordingly? Don't get me wrong, he had some good input but there are other ways, and maybe better, options. So, what cam, fuel pump, distributor, and IAC do you have? Did you go with quality parts or buy cheap replacements?

Do you have a fuel pressure gauge or are you going by the "advertised" 18 LB spring (probably from SPR Performance when you bought the 46mm TB from them)? Can you check fuel pressure while under load? A WBO2 is IMHO crucial for tuning "performance" systems.

Why do you have your base timing set at 2° when TBIchips should have set SA tables in his calibration? BTW, FWIU Harris retired a couple years ago, due to health issues, and someone else is running TBIchips.com

As I said, data logging is a great plan

Don't get me wrong, I've been there, done that, never could get mine running right until I explored other avenues. At least you hopefully have the faster (8192 baud as apposed to 160) '7427 which has expanded tables for better performance. My 7747 just couldn't keep up.

At least it was a helluvan education for me, still learning every day

HTH

My cam is Chevrolet performance 14097395, distributor is a Delphi for a ‘92 z28 Camaro, vortec fuel pump can’t remember the brand. The truck is a fresh build so everything has been on for less than 5000km. I always get acdelco or Delphi or genuine parts, I want to try messing with the fuel pressure I think 18 is too much which way do I turn the regulator to get more/less? I don’t have a way of checking it under load at the moment and my timing is 2 degrees advanced just because it seemed happier there but I will be putting it back at 0 to see if it changes anything.

 

[Marcus W]

My cam is Chevrolet performance 14097395, distributor is a Delphi for a ‘92 z28 Camaro, vortec fuel pump can’t remember the brand. The truck is a fresh build so everything has been on for less than 5000km. I always get acdelco or Delphi or genuine parts, I want to try messing with the fuel pressure I think 18 is too much which way do I turn the regulator to get more/less? I don’t have a way of checking it under load at the moment and my timing is 2 degrees advanced just because it seemed happier there but I will be putting it back at 0 to see if it changes anything.

Yep, there's folks on www.gearhead-EFI.com that do. Dave w (Old School EFI) for one. He'll have you data log, tune, data log, rinse and repeat.

Let's ensure your sensors, ignition, and fuel delivery are all good 1st. No amount of tuning will mask an inherent mechanical issue.

Let me guess, you read Brian Harris' recommended 350 TBI mods and built yours accordingly? Don't get me wrong, he had some good input but there are other ways, and maybe better, options. So, what cam, fuel pump, distributor, and IAC do you have? Did you go with quality parts or buy cheap replacements?

Do you have a fuel pressure gauge or are you going by the "advertised" 18 LB spring (probably from SPR Performance when you bought the 46mm TB from them)? Can you check fuel pressure while under load? A WBO2 is IMHO crucial for tuning "performance" systems.

Why do you have your base timing set at 2° when TBIchips should have set SA tables in his calibration? BTW, FWIU Harris retired a couple years ago, due to health issues, and someone else is running TBIchips.com

As I said, data logging is a great plan

Don't get me wrong, I've been there, done that, never could get mine running right until I explored other avenues. At least you hopefully have the faster (8192 baud as apposed to 160) '7427 which has expanded tables for better performance. My 7747 just couldn't keep up.

At least it was a helluvan education for me, still learning every day

HTH

As for my iac I cannot get the base idle set properly, it’s just a new one that was in the throttle body when I received it, then I swapped it for the almost new one in my old tb, correct me if I’m wrong but the procedure should be
Jump A and B
Turn key on, wait 30 seconds, unplug iac
Start vehicle, adjust to 650 rpm
Turn off the truck, unplug the A and B, disconnect battery for 30 seconds

 

[PlayingWithTBI]

I want to try messing with the fuel pressure I think 18 is too much which way do I turn the regulator to get more/less?

Is your regulator adjustable? Anyway you unscrew (rightey tightey, leftey loosey, ha ha) to reduce pressure. here's an example of an AFPR and pressure gauge.

You must be registered for see images attach

Here's one with an 18 LB spring set at 20 PSI. With this setup I can adjust that spring from 15 - 20 PSI.

You must be registered for see images attach

This is why you want a WBO2, to get your VE and PE AFRs right.

As for my iac I cannot get the base idle set properly, it’s just a new one that was in the throttle body when I received it,

If you're having issues getting it down to your base idle, odds are you have a vacuum leak somewhere.

Turn key on, wait 30 seconds, unplug iac
Start vehicle, adjust to 650 rpm
Turn off the truck, unplug the A and B, disconnect battery for 30 seconds

Yes, pretty much but, without a scanner you can't see what you IAC is being commanded after you set base idle.

There's another way to do it - with a scanner you can see what your IAC is being commanded. Then adjust min idle screw until you see it at 10 to maybe 30 counts, AND you idle maintains desired RPM by the PCM. Do not let your ICM be commanded to zero counts, it may burn up the stepper motor by doing that.

My cam is Chevrolet performance 14097395

18 PSI s/b OK if your VE tables are tuned properly. I prefer to tune the tables than play with spring pressure until it's out of range.

vortec fuel pump can’t remember the brand.

ACDELCO EP381 is the go to pump for your application.

my timing is 2 degrees advanced just because it seemed happier there but I will be putting it back at 0 to see if it changes anything.

Again, this s/b done in the calibration.

Enjoy!