GM 98 5.7 Vortec help with tune

[andyh]

Hello,

I have a 98k15 that i am trying to get running normal. I recently rebuilt the engine and added a cam to it. After the rebuild the engine runs great but i have a strange thing happening. The first start every time fires right up and idles perfect. The second and every start after unless it cools down has a stumble rough idle for 10 seconds. It usually requires throttle input on the second/third start to start. once it starts you have to add throttle for 10 seconds. then after that it idles normal and continues to run normally. I have swapped the stock injector to the MPI. I am sure this is related to the cam. I am not much of a tuner being upfront about that. Any suggestions would be appreciated.

[bk2life]

I have swapped the stock injector to the MPI.

can you please explain this a bit more in detail?

Also your PE is odd as well as your VE tables. -neither of these will help your start up issue.

Need to know more about the injector info, and then we can move on from there.

[andyh]

Yes it was swapped from the typical CSFI spider injection to the MPFI. Still a spider but has the injectors at the end of the spider right at the intake instead of the tappits. Before the rebuild with the MPFI truck ran fine. Now with the rebuild i upgraded the CAM. It is large but was the only one suggested by Summit/Jegs for a Vortec stock set up. You can see the MPFI set up here. https://www.motormanfuelinjection.co...onversion.html so when we start anytime after the first start of the day the truck doesn't want to idle on it's own without a little throttle being added for about 10 seconds every time. When the 10 seconds is over truck runs fine and has no other issue. I will find the data on the cam i know it was close to 515/489 but i can't remeber exact. I will find it and add it here. Seriously thank you in advance!