Surging Idle

[gcwh02]

Just put in this new engine and it runs great except for when I'm coming to a stop. When I take it out of gear and brake to a stop, the rpms will jump from 500 to 1300 and then it will stall. Sometimes it will stop and idle just fine around 800-900. Anyone know whats up with this?

 

[88_GT_5_oh]

did you go through the sticky at the top of the page?

http://forums.stangnet.com/showthread.php?t=534062

 

[TENGRAM]

Just put in this new engine and it runs great except for when I'm coming to a stop. When I take it out of gear and brake to a stop, the rpms will jump from 500 to 1300 and then it will stall. Sometimes it will stop and idle just fine around 800-900. Anyone know whats up with this?

the cylindrical thing on the frontside of your throttlebody is the Idle Air Control Valve (IAC). it is responsible for preventing stalls when coming to a stop and also it keeps the idle steady. you probably just need to remove it and clean it out with carb or throttlebody cleaner. if that doesn't fix it, might want to replace it.

other possibilities are your Vehicle Speed Sensor or you have a vacuum leak.

 

[gcwh02]

thanks for the replies. The only thing about that IAC is that it ran fine on my old setup. I was told it was something with having to adjust my TPS? i dont know...

 

[jrichker]

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=534062
for help with your idle problems. The first post contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.