car idles fine till gets warm and then idle goes up and down up and down up and down and wont stop, could this be cause there is not enought antifreeze, or water, or is the O2 sensor broken , this is open header no exhaust and i have no check engine light ?? any one know why its idle liek that

 

mine did that when i had a vacume leak

 

how do i know if i have a vaccum leak

 

my car did the same thing after my mpfi swap. so after reading through all the idle prob. posts on this website ive learned that it could be vacum leaks, air pockets in the coolant., dis-calibrated tps semsor and a dirty or misfunctioning eacv. I bled my coolant lines and submerged my eacv in carb cleaner and now it idles a lot better; it still has a small prob where it takes a while to come down from 2000rpm to 800 but i still havent repositioned my tps sensor. i think there are more troubleshooting tricks out there but these are the only ones i can remember right now.

 

what about o2 sensor

 

I just had this problem not too long ago and all I did was change my spark plugs to Denso from NGK and it idles sweet. The NGK spark plugs I took out looked like it was dipped in black asches.

 

I had the same problem with my HF engine. I worked fine most of the time but then out of nowhere...surging up and down...It did not affect acceleration at all, only when it was at an idle. I wis I knew....

 

spark plugs effect idle ??

 

dood did u ever fix it?

 

Yea......All I did was change the spark plugs from the current NGK that the previous owner had in there to Denso's and it went away. I got the normal Denso ones...nothing extreme like platinum or anything!

 

reset your ecu.. warm up car. pull the "hazard" fuse under the hood for atleast 10 seconds.. put it back and start it up..

this happened to me a lot and this fixed it

 

I answered this quesiton in a post last night. When my car did this I was using 87 octane gas, I switched to using the middle grade stuff here, 89, and it fixed my problem. I would also advise a tune up if you havent done so in a while.


[Modified by ijjz, 3:43 PM 9/16/2002]

 

MAP Sensor - I replaced 2 this weekend as the first one I bought was bad too. If youpull the hose off the bottom of the MAP only - the idle should steady. I also had the other end of the line hooked to the carb instead of the manafold by accident. this made a dif as well

 

o2 sensors have nothing to do w/ idle

 

your idle adjustment screw is letting too much air in, and the EAVC can't compensate, so it's searching for the idle. try adjusting it some more, and resetting the ECU.

 

where is my idle adjusting screw

 

right above where the intake tube attaches to the throttlebody on top.

 

i tryed adjusting the fast idle valve but it didnt work i have no check engine lights if my map sensor was bad wouldnt it throw a code and check engine light?? also where is my EACV sensor

 

my bro had the same problem w/ his s-10. he took it to the dealer and said it was clogged fuel injectors. worth a shot.

 

It can only be two things.

1: Vacuum leak

2: EACV is bad (This is most likely the case)

I had this EXACT same problem when I swapped to my Y8 intake manifold. I replaced the EACV, idle is perfect now! Mine rpms went from about 1,200 to 2,000.
Up and down, up and down and it wouldn't stop. And it only did it after the car warmed up.

EACV's usually just don't die on their own. Mine was bad because it was kinda smashed during shipping. But they can break by other means too. How long have you had this problem? What have you done to your car recently? (mods, anything)

The EACV controls the idle speed by opening/closing an air bypass past the throttle plate. You'll also notice that the EACV has two coolant lines connected to it. These lines actually heat up the EACV, so it can begin adjusting it's little valve. So when the motor is cold, the EACV is automatically at wide open. When it starts heating up, it will slowly close this valve off little by little, and once it's at the normal operating temp., the valve is supposed to balance the idle speed based on the engine load (like if your lights are on, or AC is on, the EACV will let a little more air through, increasing idle speed). If the delicate internals are damaged somehow, the EACV will have a hard time fine tuning the idle, so it will just bounce up and down.

Spark plug, wires, cap/rotor, 02 sensor, low radiator fluid, injectors NONE of these are gonna make your car idle like that.

The ECU could be bad as well, but I <U>really</U> doubt that that would be the case.


[Modified by MrTodd, 11:32 PM 9/19/2002]