not sure what it could be. only at cold start my car's idle bounces at 1500 rpm for almost exactly 10 minutes then the thermostat opens and it idles down and runs perfect. i tried adjusting the tps but that didnt help its where it supposed to be and the ecu is shooting a iac sensor code but the car has always shot that even with the other motor i had. i put a good iac sensor on but it still idles bad. any ideas on what it could be? thanks

 

You know without knowing the engine or engine managment that you are running I will take a shot at it. I know with hondata and the coolant lines removed from the IAC and TB my idle did the same thing, so I adjusted the screw on the TB that allows more or less air to bypass the TB at idle.

 

thnkas for the info sorry its a sohc vtec. ill try messing wiht that agian. did it only do that when it was cold start tho? and did it take your motor 10 minutes to get warm? its completly fine after it idles down. but thanks ill try it out

 

one question, do you have the fast idle thermo hooked up? this is the coolant passage that runs from the intake manifold to the throttle body. if so you need to adjust the screw inside of the housing. there are 3 8mm bolts on the side closest to the firewall, inside you will see a spring loaded plastic assembly in which can be adjusted with a flathead screwdriver. see what happens is over time the spring somehow loses tension and the valve fluctuates with cold coolant, once warm or hot coolant passes through the valve it expands closing the fast idle valve and then uses the auxilary air valve to fluctuate idle speed as well as the air idle valve.

 

thanks! you are talking about the housing on the throttle body where the coolent lines hook up at right? ill take a look thanks for the info this has been pissing me off

 

its ethier throttle sensor or o2 sensor

 

Is it just idleing high while it warms up? If thats the case, its supposed to do that...

 

i siad it bounces at 1500 for 10 minutes

 

so it doesnt stay at a steady 1500?

 

no