88 S4 hunting idle stalling issues
06-26-2015, 04:21 PM
#16
Rennlist Member
If the TPS is not registering closed contact the ISV will not work and the default [rest] position relies on the static aperture of the zero position of the ISV which is sized to give a stable tickover when the motor is warm.
If the ISV is not working at all you will have problems with cold start that will require a light throttle opening to get the motor to fire up.
If the ISV shuttle is sticking the controller will demand more opening signal be applied and then may apply too much correction creating a hunting effect.
If cold starts are no problem then I would think the chances are it is an ISV problem. You can also also check to ensure the ISV connector is correctly seated.
Rgds
Fred
If the ISV is not working at all you will have problems with cold start that will require a light throttle opening to get the motor to fire up.
If the ISV shuttle is sticking the controller will demand more opening signal be applied and then may apply too much correction creating a hunting effect.
If cold starts are no problem then I would think the chances are it is an ISV problem. You can also also check to ensure the ISV connector is correctly seated.
Rgds
Fred
06-26-2015, 05:08 PM
#19
Drifting
What's the condition of the O2 sensor? Bad or no adaptation will screw up the idle. Codes?
The S4 LH2.3 ICV armature is spring loaded. The LH just pulses it open, unlike the S3 LH2.2 which has to pulse its ICV open and pulse it closed.
In its resting position the S4-up ICV has a default opening like you see there. The S4 ICV rotates from the default position past fully closed to its fully open position. The default opening is a failsafe which the S3 type ICV does not have.
The S4 LH2.3 ICV armature is spring loaded. The LH just pulses it open, unlike the S3 LH2.2 which has to pulse its ICV open and pulse it closed.
In its resting position the S4-up ICV has a default opening like you see there. The S4 ICV rotates from the default position past fully closed to its fully open position. The default opening is a failsafe which the S3 type ICV does not have.
Adrian
06-27-2015, 06:37 AM
#20
02 sensor or bad grounding on the temp sensor I would hazard from my own experience with a similar idle issue when i first had my car. As suggested disconnected the battery, then o2 sensor and see how she runs on base no cat maps. Weirdly, another issue which effected my warm idle was the air filter being the wrong way up.
06-28-2015, 09:53 PM
#21
Three Wheelin'
What relationship does the 02 sensor or temp 2 sensor have with the car being in gear or when braking hard. The problem seems to persist while in gear only and foot on pedal and would only stall when braking really hard like slamming on the brakes.