This might be the culprit. A vacuum leak more than likely leads to a surging idle.

 

Since you changed the throttle body you need to check these two things:

1. Idle screw adjustment (located on throttle body)
2. Make sure the throttle cable has some slack in it and the throttle plate is allowed to "close" at idle.

 

threw a code today PO507...Idle Control System RPM Higher Than Expected ---- wow that helps
double checked all my vacuum lines and their all hooked up felt around for any tears and didnt feel any- egr was hooked up correctly-- I did however bypass the coolant lines for the throttle body so it could be sticking but ive taken my hand and actually pulled on the lever to make sure its shut!

 

the screw adjustment is set at the lowest setting- highest goes up over 2500 rpms, cable has plent of slack- and throttle body is brand new so it should be clean-- I thinking it may be over ported and cause to much air to sneak by- I guess i have to throw in my old stock one and see this weekend

 

ahh... I believe your car thinks its forever in warm up mode then. Try hooking the coolant lines back up and see if the idle dips down after the car is warmed up.

 

yaah that does make sense- but theres no temp sensor in the throttle body- ohh well ill try it anyways! I appreciate all the helpfull suggestions guys!

 

This would be true....if he bypassed the thermostat. Your throttle body might be over ported or it isnt closing all the way. Just switch back to the stocker and see if you can narrow down the culprit.

 

thatsMR2u, is your idle high even when the engine is cold? I also have a small issue with my car idling at 1600-1800 rpm but only when the engine is warm/hot. It will idle at 800-1000 rpm (lopey) when cold, and after being driven for a while sometimes the idle will stay around 1700 rpm, but not always.

Just wondering whether I have the same issue and if I should do the same checks as you did...

My car has HKS 272s, HKS intake, hallman mbc, stock bov, walbro 255, and hks ti exhaust with cat delete.

 

this is going to sound really dumb but is your vent set to defrost or defrost and vent to floor? That will turn on the A/C compressor and make your idle go haywire.

 

I can almost guarantee this isn't related to his (current) tune or lack thereof.

 

anja ive tried all durations of AC on and off - the AC on it almost even makes it idle a little better....
Mostro- my problems is the opposite of yours- yours almost sounds like a temp sensor or your thermostat- what are you running diverter valve or vent to atmosphere?

Even tho I havnt thrown a check engine code im thinking the EGR valve is staying stuck open

 

if it isn't the AC, in my experience, erratic idle like yours is usually caused by vaccum leak at the TB.

 

The car is still on the stock bov, so I imagine that it is a recirc instead of vta. In my case, turning on the AC also bring the idle to about 1000 rpm. No CEL light either.

 

I think that is your best bet right now , for what ever reason it sound like its not closing all the way . btw do you have a S-afc(or some way of loging TPS) if so what is the throttle position % ? 0% ?

 

nope no way to log TPS, if the old throttle body doesnt work im going to have to go see a friendly dealership and use the MUT II scanner to adjust the throttle