Gen V LT1 wont idle after engine rebuild - vac leak? something else?
09-17-2018, 01:34 PM
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Gen V LT1 wont idle after engine rebuild - vac leak? something else? Hi All,
I have a 2014 C7 Z51 (Gen V LT1) which I recently had rebuilt with the following parts:
Vengeance Racing Pistons
Vengeance Racing Stage 3 Cam Kit (Cam + valve springs, timing chain, LS7 lifters, Cam phaser limiter, ARP bolts, pushrods..etc)
LT4 High Pressure Fuel Pump
LT4 Injectors
Long tube decatted headers + x-pipe
Since I got the car back I have not been able to get it to idle correctly. The car fires up and then almost immediately bogs down and stalls. If I can catch it with a bit of throttle, I can keep it alive at 1000rpm. If it dips below this it starts shaking and stalls. The higher the RPM's, the smoother it gets.
There are no CEL's, and my tuner has mapped the car for all my mods and after sending him several log files he is starting to think that the problem is with the engine, not the tuning.
I have been working on the theory that it might be a vacuum leak as the symptoms satisfy most of what I am seeing. However I have checked and replaced every visible vacuum hose, and sprayed carb cleaner around pretty much everything post MAF that might leak. I have also tried running the car without the MAF connected so it goes into SD mode, but it runs even worse like this. I have purchased some smoke bombs to see if I can make a home-made smoke machine, but I will have to report back on that when I get the parts I need.
My tuner asked me to check whether the car is firing on all cylinders - but as it is almost impossible to keep running as it is, I don't think unplugging coilpacks is going to give me any clues. Could I instead maybe measure the temperature of each exhaust header to see if they are all roughly the same temp?
I'd really appreciate any help you guys can offer with diagnosing this.
Thanks
I have a 2014 C7 Z51 (Gen V LT1) which I recently had rebuilt with the following parts:
Vengeance Racing Pistons
Vengeance Racing Stage 3 Cam Kit (Cam + valve springs, timing chain, LS7 lifters, Cam phaser limiter, ARP bolts, pushrods..etc)
LT4 High Pressure Fuel Pump
LT4 Injectors
Long tube decatted headers + x-pipe
Since I got the car back I have not been able to get it to idle correctly. The car fires up and then almost immediately bogs down and stalls. If I can catch it with a bit of throttle, I can keep it alive at 1000rpm. If it dips below this it starts shaking and stalls. The higher the RPM's, the smoother it gets.
There are no CEL's, and my tuner has mapped the car for all my mods and after sending him several log files he is starting to think that the problem is with the engine, not the tuning.
I have been working on the theory that it might be a vacuum leak as the symptoms satisfy most of what I am seeing. However I have checked and replaced every visible vacuum hose, and sprayed carb cleaner around pretty much everything post MAF that might leak. I have also tried running the car without the MAF connected so it goes into SD mode, but it runs even worse like this. I have purchased some smoke bombs to see if I can make a home-made smoke machine, but I will have to report back on that when I get the parts I need.
My tuner asked me to check whether the car is firing on all cylinders - but as it is almost impossible to keep running as it is, I don't think unplugging coilpacks is going to give me any clues. Could I instead maybe measure the temperature of each exhaust header to see if they are all roughly the same temp?
I'd really appreciate any help you guys can offer with diagnosing this.
Thanks
