ok i rebuilt and installed my ls motor this weekend. after initial startup, the idle was fine. we filled it up with coolant and revved it up and as soon as it got to about 1k rpm the revs would start fluctuating, kinda like a rev limiter. it will do this until about 25-3k rpm and then it will smooth out. i never had a problem with this before the rebuild. checked all of the vacuum lines and made sure that all of the sensors were hooked up. i also put in a nwe ste of plugs when i did the rebuild. i have put about 60 miles on it and it is still doing it. any ideas?

 

anyone?

 

i will try to get video of it in a bit. until then any ideas?

 

check the sensor under your throttle body for your cold start. you can check by putting your finger over the bottom hole in of your throttle body. it should idle normal if that is your problem