what could cause an idle surge, but only on cold starts? every morning, my car idle surges until the rpm's drop down to 700 rpm's and then it stops surging. i noticed it for the first time when i was working on the secondary air pump but everyone insisted that the SAP has nothing to do with vehicle performance so i'm assuming that it has nothing to do with the surge at all. so what else can cause this surge only at higher rpms?

 

bump

 

Its just becuase the engine is cold. If you just mean the idle is high in the morning when you start it thats fine. However if your saying that the idle is real high then drops then goes high again that could be a bigger problem.

 

If, on a cold start, your tach shows about 1200 rpms and then drops down to 700-800 (whatever's normal for your car), then that's normal and it's the SAP working.

 

no no, i know cars idle higher on cold starts, thats not what i'm talking about. during the cold start period when the car is idleing higher, it idle surges also. i start it up, it revs to about 1200 or so, then drops to 900, then back to 1200 then back to 900....does this for about 30 seconds and then perminantely drops to around 700 after it warms up some. after the rpms drop to 700 and stay there, they dont surg anymore. it only surges in the first 30 seconds on cold starts. what could cause it to surge on cold starts but not surge anymore after the rpms drop to normal???

 

Does the idle stabilization coincide with your SAP shutting off? Also, scan for codes.

 

the only code i'm throwing is "secondary air injection system incorrect flow". i have had that code for a long time though and it only started having this idle surge issue when i took out the secondary air pump to look at it. my pump is shot and i was looking for a new one, but i ordered the resistor instead to trick the ecu into thinking the pump is working (i dont have emissions testing). so i guess to answer your question, my SAP never comes on so no it doesnt coincide with it shutting off.