Vortec 454 Revs up high then dies HELP!!

[Brice Edwards]

That's not helping. Probably need to resolve that before going any farther. You said you replace the FPR right?

Yes I replaced the FPR

 

[Tom P]

And your still having the same exact symptoms as described earlier? Sounds like it has a cam and falls on its face when you give it pedal?

I suppose it’s possible that the Bosch injectors are more sensitive to low pressure than the Multecs I have. You may very well need to get your pressure up to spec for those injectors to fire properly.

 

[Christian Steffen]

They should fire fine, but not as much fuel will be injected as what the computer is expecting, so it shows lean on the o2s. The short term fuel trims still show positive 25?

 

[Brice Edwards]

They should fire fine, but not as much fuel will be injected as what the computer is expecting, so it shows lean on the o2s. The short term fuel trims still show positive 25?

yep, positive 25 at idle. is it possible that my o2 sensors are bad?

 

[Tom P]

I quickly went back through the thread and didn't see anything about replacing O2 sensors. How long ago was that done if ever? Its quite possible that they are the culprit here. Being dowsed with un-burned fuel can shorten their life. It could explain the trims. You could start by unplugging them to see if anything changes.

 

[Brice Edwards]

Would it possibly make it run better with them unplugged?

 

[Tom P]

If you unplug them the truck will go in to a sort of "limp mode" where it just uses its best guess to monitor fuel trims. Try unplugging them and then doing another battery disconnect to get a fresh set of trims. You should see a CEL within a few minutes if not sooner. If it appears to run better, you have your answer. If no change then we move back to fuel pressure...

 

[Tom P]

I cannot remember if they have any effect in open loop mode though, so Its possible my hypothesis is incorrect since your truck is showing symptoms at cold start up.

 

[Christian Steffen]

If you unplug the 02s, it should error out as o2 sensor low activity, then it'll run open loop so it might run a bit better. With your fuel pressure low it will likely run rough still since it will be lean, somewhere around 15%. A wideband 02 would be nice to confirm if the o2s are actually correct.

 

[cool_as_crap]

To the point where it sounds like it has a cam at idle and if its idling any lower then 1k and I give it gas, it bogs down and almost dies

I've had that issue that turned out to be a vacuum leak.
Did you make sure the vacuum line at the back of the fuel rail was hooked up?
Any leaks in the EGR system?

I suggest starting fluid method to find any leaks, if you haven't already tried. And check the air hose before and after the TB.