hot start surge

[legalize420]

i noticed that whenever the car is hot enough for the fan to come on, it will surge when i start it. other than that the idle is perfect. doesnt surge or hunt at all. i think it is related to the fan and charging system. as soon as i hear the fan the volt gauge drops down and goes back up a little. the gauge even goes down when i roll down my window. i have underdrive pulleys and i was thinking about getting an overdrive pulley for the alternator. anyone ever use one? my first thought was to upgrade the alternator to a higher output but i guess i could try the pulley or even go back to the stockers. what do you guys think?

 

[legalize420]

btw, the alternator charges fine under load.

 

[HISSIN50]

If you think an OD pulley will help, I'd start it when it's going to act up and hold the idle at about 1200 RPM and see how it acts. If the issue is still there, chances are that OD'ing the alt will not fix the issue.

The voltage drop issue you have is one reason the computer uses a 5 volt, low current VREF - it takes fluctuations like this largely out of the equation.

Good luck.

 

[1TallMF]

I only had that hot start idle surge thing happen to me once, as an isolated incident that only lasted about 10 seconds. Not sure what caused it, but the fan coming on is a good theory.

 

[94gts]

my car is h/c/i and untuned. on hot starts it takes a while to crank (i have to put my foot into the gas pedal) and the idle is often a little funky once i get it started. then it calms down

 

[legalize420]

i just wanted to add that if i set the idle up at about 900 rpms it will start up and usually settle within a second or two. if its any lower it will surge and die(only when its hot). if i hold the throttle or drive the car right away it will stop surging. this did not just start to happen. i just wanted to get some other opinions. i guess im going to swap to an overdrive pulley and see if it helps.