# 2005 Pontiac G6 - runs great till it warms up **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** pontiac\ **Created:** [April 29, 2020, 10:58am UTC](https://community.cartalk.com/t/2005-pontiac-g6-runs-great-till-it-warms-up/163544 "2020-04-29T10:58:28Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![smithkyle1941](https://avatars.discourse-cdn.com/v4/letter/s/b9e5f3/32.png) [@smithkyle1941](https://community.cartalk.com/u/smithkyle1941)\ **Post date:** [April 29, 2020, 10:58am UTC](https://community.cartalk.com/t/2005-pontiac-g6-runs-great-till-it-warms-up/163544/1 "2020-04-29T10:58:28Z")
For the first five min. it has great power when i put my foot in it it just takes off fast. As soon as it warms up it starts misfiring,backfiring i have to feather gas peddle to keep the power going. If i put my foot in it it just makes it worse. the check engine light is on solid when cold then starts flashing when it warms up. it does show four codes: P0301 #1 cylinder misfire, P0452 fuel tank pressure sensor/EVAP, P0463 fuel level sensor "A"circuit high, P0461 sensor reference voltage A circuit/open. the car was hit in the front needed fender, hood and radiator. what baffles me is how and why does it run so well cold then so poorly when its warm. no water issues. any one heard of this? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [May 1, 2020, 12:08am UTC](https://community.cartalk.com/t/2005-pontiac-g6-runs-great-till-it-warms-up/163544/2 "2020-05-01T00:08:46Z")
> [@smithkyle1941](#): > > what baffles me is how and why does it run so well cold then so poorly when its warm. no water issues. any one heard of this? When the Check Light is solid when the engine is cold, it means a major misfire isn’t occurring. When the Check Engine light starts flashing, it means a major misfire is occurring. > **[Check Engine Light Flashing](https://www.innova.com/pages/check-engine-light-flashing)** > > Check Engine Light Flashing? Here’s how to fix it. A check engine light that’s flashing is up there with one of the most daunting sights that anyone with a vehicle can see. And what makes a blinking check engine light even worse is the damage done to... Tester ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [May 1, 2020, 2:18am UTC](https://community.cartalk.com/t/2005-pontiac-g6-runs-great-till-it-warms-up/163544/3 "2020-05-01T02:18:54Z")
The other thing is that when an engine is cold, it it running in open loop mode and using pre-set sensor information from the computer. Once it warms up it goes into closed loop and uses the actual readings from the various sensors. Really time to have someone look at it though for a good diagnosis. On mine it only took a few minutes of mis-fire to ruin the $700 cat.