IAC Delete or Drive by Wire? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

richierichness · 01-26-2017, 01:05 PM

s14 w/stock rb25 s2
q45 TB
Greddy knock off
VE tuning with Haltech Elite 2500

What are most people doing to clean up the idle on their RBs? This thing is a nightmare once the engine warms up. If I target any RPM below 1100 the idle will bounce around and eventually the engine will stall. My goal is stable idle between 700 and 900 rpm.

Steps taken so far:
-Adjusting IAC screw
-Tuning fuel via open and closed loop
-Unplugging IAC and valve
-Boost Leak Testing
-Fuel pressure is good (43 psi)
-New injectors (900 cc)
-New Battery
-New plugs gapped to .030"
-Ohms coil pack testing (hot and cold tests)
-O2 (Haltech) Wideband sensor is functioning properly (deleted oem narrowband)

Steps I have not taken yet:
-Replace Coolant Temp Sensor
-Clean IAC and valve
-Diagnostics testing for IAC,valve, or TPS (does this need to be done?)
-Clean Throttle body

Should I stop fucking with this and completely delete the IAC system?

Should I go 1 step further and do a drive by wire TB? Does anyone make a kit or parts to support drive by wire with the RB's?

KAT-PWR · 01-26-2017, 01:50 PM

Battery voltage offset issue making timing go crazy trying to idle compensate?

ultimateirving · 01-27-2017, 02:47 PM

Ok first take the iacv off and clean it. These things can get gummed up and cause it to function poorly.

richierichness · 02-04-2017, 03:37 PM

I've replaced the coolant temp sensor and IAC... still having issues.

Sent from my iPhone using Tapatalk

Kingtal0n · 02-04-2017, 05:21 PM

If I have a car giving me trouble with an idle, the first thing I do is disable the IACV completely and boost leak check the engine for pressure leaks. If it still bounces around, the next step is disable the timing control (lock the timing steady). If the engine is still having trouble, manually verify the locked timing for each cylinder using 90* timing marks to ensure each one is sparking at the right moment. Then, you are looking for combustion related issues, fuel pressure, checking spark plugs, cleaning injectors, time to start thinking about a camshaft related issue or other airflow related source that is not controlled by the computer.

Then work backwards. Once the idle is stable with a locked timing and no idle control motor, you enable the timing and tune the map for stable idle control timing. Then you add back the IACV function and tune that. The idle control motor is the icing on the cake; shouldn't need one to maintain a steady idle, it just helps raise and lower the idle for temperature, any added idle control function is a bonus feature (icing). You should not be looking at it for idle stability as a sole, primary function. That just turns it into a bandaid, the opposite of icing.

01-26-2017, 01:05 PM	#1
richierichness Join Date: Oct 2015 Location: Virginia Age: 36 Posts: 29 Trader Rating: (0) Feedback Score: 0 reviews	IAC Delete or Drive by Wire? s14 w/stock rb25 s2 q45 TB Greddy knock off VE tuning with Haltech Elite 2500 What are most people doing to clean up the idle on their RBs? This thing is a nightmare once the engine warms up. If I target any RPM below 1100 the idle will bounce around and eventually the engine will stall. My goal is stable idle between 700 and 900 rpm. Steps taken so far: -Adjusting IAC screw -Tuning fuel via open and closed loop -Unplugging IAC and valve -Boost Leak Testing -Fuel pressure is good (43 psi) -New injectors (900 cc) -New Battery -New plugs gapped to .030" -Ohms coil pack testing (hot and cold tests) -O2 (Haltech) Wideband sensor is functioning properly (deleted oem narrowband) Steps I have not taken yet: -Replace Coolant Temp Sensor -Clean IAC and valve -Diagnostics testing for IAC,valve, or TPS (does this need to be done?) -Clean Throttle body Should I stop fucking with this and completely delete the IAC system? Should I go 1 step further and do a drive by wire TB? Does anyone make a kit or parts to support drive by wire with the RB's?

01-26-2017, 01:50 PM	#2
KAT-PWR Nissanaholic! Join Date: Dec 2011 Location: US Posts: 2,040 Trader Rating: (11) Rides Gallery: KAT-PWR Feedback Score: 11 reviews	Battery voltage offset issue making timing go crazy trying to idle compensate? __________________ MRP Manufacturing

01-27-2017, 02:47 PM	#3
ultimateirving Zilvia FREAK! Join Date: Nov 2010 Location: arizona Age: 33 Posts: 1,519 Trader Rating: (1) Feedback Score: 1 reviews	Ok first take the iacv off and clean it. These things can get gummed up and cause it to function poorly. __________________ Z32 with lq4 swap Desert Street Scene \|\| Dssevents.com

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02-04-2017, 03:37 PM	#4
richierichness Join Date: Oct 2015 Location: Virginia Age: 36 Posts: 29 Trader Rating: (0) Feedback Score: 0 reviews	I've replaced the coolant temp sensor and IAC... still having issues. Sent from my iPhone using Tapatalk

02-04-2017, 05:21 PM	#5
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,648 Trader Rating: (17) Feedback Score: 17 reviews	If I have a car giving me trouble with an idle, the first thing I do is disable the IACV completely and boost leak check the engine for pressure leaks. If it still bounces around, the next step is disable the timing control (lock the timing steady). If the engine is still having trouble, manually verify the locked timing for each cylinder using 90* timing marks to ensure each one is sparking at the right moment. Then, you are looking for combustion related issues, fuel pressure, checking spark plugs, cleaning injectors, time to start thinking about a camshaft related issue or other airflow related source that is not controlled by the computer. Then work backwards. Once the idle is stable with a locked timing and no idle control motor, you enable the timing and tune the map for stable idle control timing. Then you add back the IACV function and tune that. The idle control motor is the icing on the cake; shouldn't need one to maintain a steady idle, it just helps raise and lower the idle for temperature, any added idle control function is a bonus feature (icing). You should not be looking at it for idle stability as a sole, primary function. That just turns it into a bandaid, the opposite of icing.