Very strange idle issue

[keeler]

I've had a lot of idle issues and read many articles on it but this one boggles me. My car idles around 2k. I've fixed all boost leaks, I've done an air test and smoke test. I've tried to the block on the fiav, replaced TPS, IAC. Adjusted Biss, replaced ecu.
The other problem is if I go full throttle and go into neutral my car will drop to 100rpms and come close to dying or die. If I raise my idle, it will drop to 200rpms instead or 300 etc. but then it will idle at 2200rpm and so on. Any tips?

 

[FL_TalonTsi]

well for the idling at 2k, just how much did u adjust the biss screw. my car was idling at 2k when i got it, i pretty much tightened the biss screw all the way down to where it was alittle tough to tighten it, and it idled at 750 rpm. don't just make tiny little adjustments it will probably have to be significant adjustments.

 

[Clutch GSX]

Did this happen out of nowhere or was it soon after you added a mod?

 

[wont_luz]

Get yourself a can of carb cleaner...and start the car. While idling spray small bits of the cleaner around various intake matings, ie-intake mani gasket, throttle body gaskets, bov, etc...if there's a leak u couldn't find with the boost leak test u'll find it here, the motor with want to die if there's a leak. Have you tried resetting the ecu? Perhaps you need to calibrate the iac? Just my .02...

 

[Laysher91]

My first guess would be: is your throttle closed switch functioning correctly? It is the sensor on the top of the TB that the throttle lever hits. I believe this condition won't throw a CEL. Without this sensor, the ecu doesn't know when to hold idle speed (throttle closed), and instead it thinks the throttle is open and often the idle will wander. Second guess: do you have the correct TPS in your car? You should have a 3 pin TPS. A 2g 4 pin TPS will fit into the wiring harness but the sensor doesn't function properly because there is only 3 pins on the harness side.
Are your throttle cables adjusted properly? That is the starting point for idle adjustment; it is difficult to control the idle and get it within range if the cables are too tight.

 

[steve]

Also make sure that the TB is well grounded. The brass strap on the top that connects to one of the bolts into the manifold is to ground the TB. Without it the IPS doesn't really work.

 

[keeler]

Grounds are good as they've all been replaced and problem has existed for quite some time prior to any modding. Ecu has been replaced once, tps has been replaced and adjusted. At idle my throttle body is opening to what it's supposed too. I've soaked the car multiple times with carb cleaner looking for it. If I adjust my biss screw all the way down the car will idle good but when I shift gears or let off the throttle after heavy acceleration it will die. How can I recalibrate the iac?

 

[steve]

I recalibrate the iac?

You don't, you make sure that the IPS is working and the ECU sees it, then you set the BISS per the manual. The ECU will "calibrate" the ISC in operation.

Steve

 

[Evil_speedracer]

Sorry to be captain obvious, but are you grounding out the plug from the firewall behing the battery? I don't know what that plug is called but I do know it has to be grounded out or the ECU will recalibrate the idle to what it wants. I know the CAS is like this too when you set the base timing. If that is what you were doing anyhow, sorry for being captain obvious.

 

[keeler]

Sorry to be captain obvious, but are you grounding out the plug from the firewall behing the battery? I don't know what that plug is called but I do know it has to be grounded out or the ECU will recalibrate the idle to what it wants. I know the CAS is like this too when you set the base timing. If that is what you were doing anyhow, sorry for being captain obvious.

I know what you're talking about it's setup right. I honestly love DSMs but i've never been able to figure this out on this car. I have a Conquest and another AWD 2g. I'm going to get a new biss screw and gasket, and do another TB gasket and see what it'll do. The A/F's are perfect and the timing is correct.

 

[keeler]

Okay I got the idle down via messing with the Biss and the idle switch. However now I'm getting idle surge a bit and it's idling around 1500

 

[steve]

Once the car is up to temp the BIS should be adjusted to idle at 750 RPM unless you have a modified ECU.

What did you do to the IPS?