Vortec 454 Revs up high then dies HELP!!

[Brice Edwards]

Hi there, I have a 97 Vortec 454. It had an injector stuck open so I decided to take off the upper intake and replace all 8 with some 19lbs venom injectors from summit racing. Now every time I start it up. it shoots straight to 3500rpm for 3-5 seconds then dies. The only way to keep it alive is to pump the gas like crazy and it'll just go right back to 3500. I've checked for vacuum leaks and changed a few sensors but nothing will fix it and it wont throw any codes. Please help

 

[Tom P]

Welcome. So theres a few things you are going to want to look at for a base line. The over revving at start sounds like it could be fuel pressure related, so get or rent a gauge and test it. Should be in the ~56psi range. Second, the dying issue sounds like it could be vacuum leak related. When you re installed the upper plenum did you make sure the new gasket was seated properly? All the previous gasket debris was removed? What about the fuel pressure regulator? Replaced while you were in there? How did the vacuum hose from the intake to the FPR look?

 

[TKerr]

Welcome. So theres a few things you are going to want to look at for a base line. The over revving at start sounds like it could be fuel pressure related, so get or rent a gauge and test it. Should be in the ~56psi range. Second, the dying issue sounds like it could be vacuum leak related. When you re installed the upper plenum did you make sure the new gasket was seated properly? All the previous gasket debris was removed? What about the fuel pressure regulator? Replaced while you were in there? How did the vacuum hose from the intake to the FPR look?

I addition to Tom P suggestions. I notice you stayed you replaced multiple sensors. Which ones and why? This will help guys direct you.
Is throttle plate sticking? Is truck running fat (rich) at 3500 rpm? Does the fuel pump run and then shutoff with KOEO?

 

[Tom P]

What method did you use to check for vacuum leaks? Propane?

 

[Brice Edwards]

Hi there, I have a 97 Vortec 454. It had an injector stuck open so I decided to take off the upper intake and replace all 8 with some 19lbs venom injectors from summit racing. Now every time I start it up. it shoots straight to 3500rpm for 3-5 seconds then dies. The only way to keep it alive is to pump the gas like crazy and it'll just go right back to 3500. I've checked for vacuum leaks and changed a few sensors but nothing will fix it and it wont throw any codes. Please help

Yes I made sure multiple times the intake gasket sealed properly. All left over materials were removed. The FPR was replaced and the vaccum hose looked perfect.

 

[Brice Edwards]

I addition to Tom P suggestions. I notice you stayed you replaced multiple sensors. Which ones and why? This will help guys direct you.
Is throttle plate sticking? Is truck running fat (rich) at 3500 rpm? Does the fuel pump run and then shutoff with KOEO?

I replaced the idle air valve, the Mass airflow sensor, crank and camshaft sensors. All from suggestions of friends on how to fix it

 

[Tom P]

Pretty sure you’re supposed to have the ECM reprogrammed after changing the crank position sensor. That could be your culprit.

 

[Brice Edwards]

Pretty sure you’re supposed to have the ECM reprogrammed after changing the crank position sensor. That could be your culprit.

Possible but it was acting the same way before it was replaced

 

[Tom P]

Time to check fuel pressure I guess.

 

[Christian Steffen]

Hi there, I have a 97 Vortec 454. It had an injector stuck open so I decided to take off the upper intake and replace all 8 with some 19lbs venom injectors from summit racing. Now every time I start it up. it shoots straight to 3500rpm for 3-5 seconds then dies. The only way to keep it alive is to pump the gas like crazy and it'll just go right back to 3500. I've checked for vacuum leaks and changed a few sensors but nothing will fix it and it wont throw any codes. Please help

Are these venom injectors supposed to be direct replacements for the stock ones? I understand they're 19 lb, but there is more to an injector than just the flow rate. What pressure were they injectors rated at? Was it 19 lbs at 3 bar or 4 bar? Are you sure they're all connected properly?

Also, what brand of sensors did you replace everything with? Unless you know for certain that the MAF was bad, I would swap back to the factory one. The aftermarket ones are generally garbage, and your MAF airflow table would likely need tuning for it.

What brand is the IAC? Again, unless you can prove the factory one was bad, I would swap back. If the issue started after the injector swap, then there is no reason to assume the IAC is the culprit.

Are all the grounds connected? Wiring all good to the IAC? Do you have something you can datalog it with? If not, probably get something.

I would be really interested to see what your TPS is reading, and also what your IAC position is at when starting. This doesn't really sound like a fuel pressure issue to me.

After the crank and cam position sensors are changed, and crank relearn procedure needs to be done, but I don't think that would make it run like garbage, just throw a code.

Also, are you sure the distributor is installed correctly?

http://www.gmtruckcentral.com/articles/distributor.html