dth0ng69

Okay so randomly, and more often now when my car is idling, it would be exactly like if someone pulled out the electric plug on the IACV. I know this because I accidently drove my car with the IACV unpluged. It is a hunting idle from ? 1000- 1500? going up and down over and over.
after I turn off the car and turn it back on its regular again, except idle still fluacate and stays kind of higher.

I know for sure when I disconnect the battery and plug it back the CEL goes away, and idle is fine. because it happens like every week or 2 weeks. More often now then before.

Okay things I did, replaced Cap, rotor, plugs, pcv valve, took out my throttle body cleaned IACV and throttle body.

I have a stock d16y7 except cold air intake.

any help suggestions tips feedback would be great.

Simkin314

Things involved with idle control:

NOTE: Any extra air will confuse the ecu thereby causing rough/hunting idle. Check all vacuum lines, electronic plugs, CELs, etc


Idle control screw (throttle body)
function: allows more or less air directly into the intake manifold thereby raising/lowering the idle.
Recommendation: adjust the idle via this screw.


Throttle body vapor purge port (throttle body)
function: depending on make/model, it allows the fuel vapor from the charcoal canister purge solenoid entrance into the intake manifold.
recommendation: this port needs sealed shut, or alternatively sealed to the vapor purge solenoid (either way, no vacuum leak).


Throttle body gasket (between throttle and intake manifold)
function: keeps the throttle/intake manifold sealed without vacuum leaks.
Recommendation: make sure its sealed, no leaks.


intake manifold air ports (intake manifold)
function: miscellaneous vacuum points (including cruise control vacuum line, fuel pressure regulator vacuum line, purge control vacuum line, *more*)
Recommendation: Make sure all the ports are sealed shut, or alternatively sealed via their corresponding vacuum lines to the peripheral devices.


Intake manifold gasket (between engine and intake manifold)
function: keeps the intake manifold/engine head sealed without vacuum leaks.
Recommendation: make sure its sealed, no leaks.


Fast idle thermo valve, FIT (bottom of throttle body)
function: allows more air into the intake manifold via a thermowax plastic insert thereby compensating for colder climates (and cold starts).
Recommendation: Depending on you global position/typical environment...open the end plate and tighten the white insert all the way, thereby allowing no air through.


Idle air control Valve, IACV (back of intake manifold)
function: controls air flow during all stages of driving, opening and closing to keep intake manifold vacuum stabilized.
Recommendation: Clean, test, alternatively replace.


Throttle position sensor, TPS (side of throttle body)
function: allows the ecu intimate knowledge of the current angle at which the throttle plate is situated. This allows the ecu to compensate for many things including idle conditions, ecu tables (ignition and fuel), etc.
Recommendation: Test the center wire (make/model dependent) with your engine off, key in the ON position. This value should be 0.5 volts closed throttle and 4.5 volts wide open throttle.


Manifold absolute pressure sensor, MAP (top of throttle)
function: allows the ecu knowledge of the current vacuum value inside the intake manifold. This value is also used in conjunction with the TPS for the ecu's control of ecu tables and the sort.


ECU, PCM, (passenger kick panel)
function: overall control of the engine and peripherals.
Recommendation: check all else first... twice.


Coolant lines
function: in this context, the coolant lines are ran through the FIT and IACV to warm the thermowax inserts in order to lower the amount of air going through the individual valves. This helps stabilize the volumetric airflow for a warmer climate/warm engine.
Recommendation: Make sure they are tight with no kinks/hard unusual bends.


Coolant
function: Cools the engine. Warms the IACV and FIT valve thereby closing the thermowax inserts.
Recommendation: Make sure your coolant is topped off an your lines of bled of air (bleed the system). This will make sure the IACV and FIT get to appropriate temperature at appropriate speeds thereby not confusing the ecu (by the quantity air throughput.


Wiring (IACV, MAP, TPS, ECU)
function: to power and read the appropriate values accordingly.
Recommendation: Check to be sure signals are appropriate, plugs are appropriately situated (i.e. it is not an uncommon occurrence in HT to have the TPS and MAP plugs switched, alternatively the IAT and IACV plugs switched). Get an electrical schematic for your vehicle/engine and test all nodes for continuity to their respective locations.



Sorry so long. I just copy and paste every time I see this question. Ignore what is unnecessary, and Good luck! P.s. if anyone has something to add please do so, so I can update my copy for future use.