Idle Problems

[Turbogst15]

Here is my problem. My car decided that it doesn't want to idle anymore. Out of nowhere it just stopped idling. First thing was i took out my isc sensor, cleaned it, and my car ran and idled perfect for about 10 min of driving then the idle went. I did it again and the same thing happened. Put in a new isc sensor and it worked for about 1 day and the same thing happened. Then i turned out my BISS screw about 3 full turns out just so it wouldn't stall out and it idles but a little rough. Sometimes it almost stalls or idles really high about 2000rpms. Once and a while it surges too. Did a boost leak check and had no leaks. Took off my throttle body, cleaned it and put my BISS screw back to normal and it idled great for about 3 days then it stopped idling again!! Got new spark plugs, no change. My TPS sensor i bought brand new and is less than a year old so i don't think thats the problem?????

Also when my car is idling all messed up my car boosts lower than normal and it knocks more than normal. Usually i pull a little less than 1 degree of knock but when the idle goes and it boosts lower than normal it gets to a little over 3 degrees of knock. I don't know what else it could be?? Please help!

 

[hdoerr]

Sounds like a vacuum leak.

 

[Turbogst15]

Thats what i thought but i did a boost leak check and there were no leaks.

 

[spoonman]

This link is very helpful.

Terry's talon idle surge

 

[Turbogst15]

Now it has a mind of its own. Sometimes it idles perfect, sometimes it idles high and sometimes it idles really low like its gunna stall out, all in the same run. It also idles different every time i start it too??

Spoonman thanks for the link, it looks like they have every possible reason why a car will not idle, i hope i find my problem there.

 

[Turbogst15]

Another thing i noticed is that if its idling high while parked like almost 2000rpms, i can rev it and it still idles high but once i put it in gear and start moving it will idle really low and sometimes stall out. Also sometimes it idles really high, even with the BISS screw screwed in all the way?? And if i unplug my isc sensor when its idleing low, high, or surging it doesn't make any difference at all, it keeps doing whatever it was doing.

 

[Turbogst15]

This morning i decided to drive my car to school so i started it up and it was idling at 2500rpms. Even after it warmed up all the way it was still at 2500. After a little while of driving it started to surge between 1400 and 2000 then a little later it went to a normal idle. It has a mind of its own!!

 

[Turbogst15]

I tested the isc and found out that its working good. I also looked inside my ecu for burnt spots and there were none (thank god). I noticed that when im idling the harder and faster i pump my brake pedal the higher my car will idle. And it still idles high and low whenever it wants. Also noticed its not boosting as high as it usually does, its about 2psi lower than normal without changing any settings on my boost controller. I did a boost leak test and there were no leaks so i have no idea what it could be??

 

[Chrono64]

This happened with my sister's car recently, and the big problem with that was the O2 sensor, just one idea that might be worth looking into.