Surging Idle

[BrandonDouglas]

So before someone links me to Terry's Talon Troubleshooting, I have read it.

Anyways, I have a weird problem, my idle is sometimes high (1800), sometimes surging between 1100-1900, sometimes only when its warm, sometimes when its cold and sometimes its fine.

Now I am about to go check a few things, first thing being the BISS screw.
My car is a 2G Talon, 2G ECU with a 6bolt swap, so do I need to follow the alligator clip scenario or can I just adjust it, let it settle and re-adjust if necessary?

If its not those things then I would suspect the ISC or FIAV although I'm not sure if my car uses 2G or 1G parts for those. A little background info is most of my vacuum lines are blocked off, but I do have 2 ports underneath my throttle body that I'm not sure what they do, they're just open. Crankcase or PCV off the valve cover is just open as well. I'm also getting a P0300 error which may be related to my rear 02 being ziptied up, this weekend it is being welded in a bung. So I'm not sure if that effects the idle..

[KevinBuckham]

95% chance it's a bad ISC.

If this happened when it was just cold, I would blame FIAV and the blockoff (or lack of it).  For the ISC you can get one from RTM Racing, but I understand there are compatible Hyundai parts as well.

[BrandonDouglas]

Just updated the original post with info about the O2 sensor.
Also sometimes when its cold it will want to stall out unless I hold the throttle.

[andrew volcz]

just to further clarify for people trying to understand the situation ...

the rear o2 was deleted in the ecu reflash, however it seems like the programming is not staying.  at times a CEL will pop up for rear o2, o2 warmer, cat. the rear o2 is zip tied up as the aem wideband sensor is in that bung.  seeing as there is no cat, ive suggested an o2 extension, and bolt the sensor back up.

i found a used isc today if needed.  Rtmracing.com has new ones as mentioned

most parts are 1g, however most sensors are 2g to be compatible with the 2g ecu.
ie: 2g coolant sensors, o2, tps

[Brett Haviland]

Main thing I would look at is if your idle switch is set (part of the tps on a 2g), and working properly.  The idle will do all sorts of crazy things if that it not set properly. There is lots of info on tuners about how to set the idle switch on a 2g.   it is running a 4 wire 2g tps right?  The 1g tps is not compatible with a 2g tps on a 2g.... Unless you wire in the 1g idle switch into the 2g tps wiring.

[BrandonDouglas]

Main thing I would look at is if your idle switch is set (part of the tps on a 2g), and working properly.  The idle will do all sorts of crazy things if that it not set properly. There is lots of info on tuners about how to set the idle switch on a 2g.   it is running a 4 wire 2g tps right?  The 1g tps is not compatible with a 2g tps on a 2g.... Unless you wire in the 1g idle switch into the 2g tps wiring.

Maybe Andrew can chime in and answer this one as I'm not sure.


I checked the BISS tonight and even screwed fully in it still surges.
On the way home from school tonight starting it up after it had been sitting all day, idles normal for the first 15 sec, then drops to 200, kicks back up, idles normal, drops down to 200, kicks back up, drops down again but this time stalls. Start it up again, idles normal for about 30 sec then starts its usual surging from 1100-1900. At this point the temp gauge is not even showing 1/4 operating temp which makes me wonder about the FIAV

[John Hartman]

yes, FIAV. Just block it off, do your self a favour. I haven't had a working FIAV on any of my DSM/Galants since I did my first blockoff.  Saves TONS of headaches, and if you correctly bypass the coolant lines, you can take your throttle body off without loosing any coolant.

But, it may also be a boost leak.

I say, block off the FIAV, really check for boost leaks and repair any that you find, set base timing, set tps, (not stop switch on your 2g, unless you have one, then set it correctly as well), check to make sure your throttle cable is not too tight.  It can be and still look like its not.

Then set your base idle speed as per the manual.

If its still doing this then, try some other things such as ISC, ECU, bad grounds, wiring etc.

[BrandonDouglas]

yes, FIAV. Just block it off, do your self a favour. I haven't had a working FIAV on any of my DSM/Galants since I did my first blockoff.  Saves TONS of headaches, and if you correctly bypass the coolant lines, you can take your throttle body off without loosing any coolant.

But, it may also be a boost leak.

I say, block off the FIAV, really check for boost leaks and repair any that you find, set base timing, set tps, (not stop switch on your 2g, unless you have one, then set it correctly as well), check to make sure your throttle cable is not too tight.  It can be and still look like its not.

Then set your base idle speed as per the manual.

If its still doing this then, try some other things such as ISC, ECU, bad grounds, wiring etc.

Do you do the free FIAV block off or buy the bypass plates?
I checked all my couplers and they all looked fine.
Base timing I assume would have been set when RG tuned it.
Throttle cable was good, had a little slack to it.

Only thing in your post I don't really know anything about is the TPS or stop switch?
I am a bit of a noob.

[Richard Steger]

tps = throttle position sensor, the electrical part on the throttle body.

[BrandonDouglas]

tps = throttle position sensor, the electrical part on the throttle body.

Oh I know what it is haha, I just don't know how to set it.

[Jordan Kruger]

logger!   

[Dave Ingraham]

Hey when you said your PCV is open, is there a line that goes to the intake manifold from the top of the valve cover?   PCV is used for idle air.      

[Richard Steger]

Sorry...   I'll let the experts reply from now on.  Did you check here... http://members.shaw.ca/costall/1000Q/  or here    http://www.vfaq.com/index-main.html

[BrandonDouglas]

Hey when you said your PCV is open, is there a line that goes to the intake manifold from the top of the valve cover?   PCV is used for idle air.      

There is 2 ports on my valve cover, one at the top of the head and it has a line that goes down to the bottom of the car, with an open end, the breather tube.
Then on the side of my valve cover the 2nd port is just open to air

[Jordan Kruger]

then the pcv wont affect your intake/ idle..