Title says it all... Did some searches, and IAC didn't come up at all (not sure why) and there aren't any real descriptive things on where its located, etc etc, so I need some help!

Thanks in advance!

-Joe

 

Joe, easy way to change involves pulling the throttle off and doing it on the bench. The iac motor is on the bottom of the throttle body. After you remove it be sure to clean out the hole with carb cleaner. Also clean the back side of the throttle blades. Use a new throttlebody gasket and do not forget to install the gasket on the iac motor. Should be a new one in the box. Easy job.

 

Pete,

Sounds good. Thanks. : )

-Joe

 

There IS no IAC module. Only the motor, Pete K referenced, above. The IAC is connected to the ECM. No module.

One addendum to Pete K's comments, be sure to retract the pintle to 1 1/8th" before you (re)install it. For more IAC info, other than your service manual, it has been discussed at length in different threads , here, as associated with idle problems. If you do a search on it, don't look for "IAC" as a part of the name of the thread, but as a "word" in a thread.

RACE ON!!!

 

My bad, I didn't use the right terminology.... Sorry CFI-EFI....

I will defend my post, however by stating that a module, as defined by dictionary.com, is: "A standardized, often interchangeable component of a system or construction that is designed for easy assembly or flexible use: a sofa consisting of two end modules. "

Since the IAC "motor" is designed for easy assemby as an interchangeable component, I therefor would surmise that the IAC motor could be defined as a module as well.

What does that mean? Nothin'... But just figured if you were going to get technical, so would I. ; )

Thanks for the help, guys ,
-Joe

 

gotta love webster.

however, the forums search function SUCKS.

 

There is a Tech Tip on it, too (I wrote it ):

https://www.corvetteforum.com/techti...D=94&TopicID=2

 

While you are at it, why not remove the IAC housing and do the coolant bypass? Also cut off the water portion of the housing.

To adjust it, start up the car and let it run till it gets hot. Use a scantool to get about 10-20 IAC counts. Set TPS and youare done.

 

I wasn't getting technical. With no more information than you gave in your opening post, *I* had no idea if you were chasing a legitimate part or not. There are plenty of people on here that have a dangerous, limited, amount of knowledge. I was just trying to help you avoid a "snipe" hunt. I don't give a snit WHAT you call it. Some people call it a "valve". Which is it's function. If you had called it a valve, I wouldn't have mentioned that there was no such thing. The MAF has a burn off module. There are many other modules in these cars. When you say you are looking for a module, how am *I* to know you are chasing a part known by another name, or a shadow? You might see if you can trade that Webster's in on a Helm's.

RACE ON!!!

 

You say Toh May To I say Toh Mah To

 

I followed the procedure in the Helms manual for removal and cleaning of the IAC and the RPM's reduced from 700 to about 600. Good luck.

 

Throttle Minimum Air Position

Tools needed:
1. Torx driver # T-20
2. Paper Clip
3. Small Punch
4. Tachometer

GENERAL NOTE: The engine should be at normal operating temperature before performing any adjustments. Never rely on the dash mounted instruments for diagnostics and adjustments. The oil pressure and temperature gauges and the voltmeter and tachometer just aren't calibrated accurately enough for diagnosis, but are a relative indication for monitoring the vehicle while driving.

For this adjustment, the transmission will be in DRIVE while you're under the hood. You will need to securely set the parking brake and block the drive wheels. It would also be a good idea to have an assistant hold the service brakes while you perform the adjustments.

In order to successfully complete the adjustment, the IAC air passages and pintle need to be clean. The throttle plates and bores need to be clean as well. If this is not the case, you'll need to remove the air cleaner from TBI engines or the intake air bellows from TPI engines to gain access to the area to be cleaned. A spray-type carburetor cleaner works well for this. Cleaning the IAC passages on a TPI/MAF engine will set a DTC, but we'll be clearing that later. With the engine idling, direct the spray cleaner into the IAC air passages and around the throttle plates. Shut off the engine and continue cleaning the throttle plates by opening the throttle manually. Once everything is satisfactorily cleaned, replace the air bellows on TPI engines. Many times, this alone can solve IAC/idle speed problems.

If this doesn't solve the problem, you may need to remove and clean the IAC stepper motor. If the IAC appears to be clean and functioning properly, continue with the adjustment procedure.

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Idle Air Control Cleaning

You can remove the IAC and service it. Remove the electrical connector from the IAC. Unscrew the IAC unit from the throttle body.

You can gently rock the pintle back and forth and allow the spring to extend it until it comes apart in your hands. Clean everything with lint-free cloths and a mild solvent. Harsh solvents can affect the insulation of the stepper motor coils. It's generally the dirt and buildup on this worm shaft that causes sluggish IAC operation.

When the worm gear on the pintle shaft is clean and dry, apply one drop of clean light oil to the shaft and work the pintle back into the rack gears of the motor by the same rocking motion. It takes a while to get the pintle back into the worm gears, but you'll get it. It is important to get the pintle fully retracted into the housing so that the pintle is not forced against the gears when reinstalling the IAC unit in the throttle body.

While the IAC is out, clean the air passages in the throttle body. The oriface in the TB where the IAC resides is the seat that the IAC valve closes against, and it can accumulate a lot of carbon, dirt, and debris. The easy way to do this is with carburetor cleaner and a small stiff brush.

When everything is clean and dry, replace the gasket if it is damaged, apply a little anti-seize to the threads, and torque the IAC to the proper specs. (13 ft/lb for '85-'89 , 30 in/lb for 1990-on.) Proceed with setting the TPS and minimum air position.

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Locate the Assembly Line Diagnostic Link connector under your dash panel. Remove the cover if it is still there.






Cut and form a paper clip into a "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' sockets.




Turn on the ignition, but DON'T start the engine. This will force the ECM into its diagnostic mode. Wait 30 seconds to allow the IAC pintle to fully extend. With the ignition still on, go under the hood, remove the electrical connector from the IAC, then turn off the ignition and remove the paper clip jumper from the ALDL. With the IAC pintle fully extended (closed) all idle air will be controlled by the position of the throttle plates. Some manuals indicate that the EST bypass connector should be disconnected for this procedure, while some make no mention of it. While timing is a factor in idle speed, the EST should only operate as a function of engine RPM, temperature, and detonation sensor inputs. To remove all doubt, disconnect the EST bypass connector is your car is so equipped. Some TBI and V-6 engines do not have this bypass connector, and therefore must be set with no regard to the EST system. The EST can be bypassed on some cars by grounding the diagnostic terminal at the ALDL and continuing with the procedure, but the fuel mixture will be skewed to the rich side, affecting idle speed as well. In any event, the minimum air position idle speed range is wide enough to allow for some variations. As always, it is best to consult your service manual for the exact procedure for your system.

Locate the Torx screw on the left side of the throttle body. It may be equipped with a protective metal cap from the factory. This was intended to discourage adjustment. If the cap is present, use a small punch to knock it out. Once the screw is accessible, start the engine and place the transmission in DRIVE. Adjust the throttle stop to obtain 400-450 RPM with the transmission in "DRIVE" on an automatic transmission car, 450-550 in neutral on a manual transmission car, rotating the Torx screw clockwise to raise speed and counter-clockwise to lower speed. Once the idle RPM is set, place the transmission in PARK and turn off the engine.

Re-connect the electrical connector onto the IAC. Start engine. Idle speed should be governed by the ECM at approximately 600-650 rpm in "DRIVE" (for unmodified cars). Idle speed in NEUTRAL or PARK is less significant, and will be higher.



Throttle Position Sensor (TPS)

Tools needed:
1. Digital Volt-Ohm-Meter (VOM)
2. Breakout jumper wires or probes (make your own)
3. AutoXray, Diacom, or similar scanner will replace the VOM and jumper wires.

Turn on ignition, but don't start the engine.

With a diagnostic scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.07 VDC.

Connect the VOM to the TPS electrical connector terminals ‘A' and ‘B'.

With a breakout jumper: Disconnect the electrical connector from the TPS. Install the breakout in-line, between the TPS and wiring harness connector. Connect the meter probes to terminals 'A' and 'B' on the connector. (‘B' is the positive connection, ‘A' the signal ground, or negative.)

With probes: If you have very slender probes on your VOM, you can back-probe the TPS connector while it is attached to the TPS. If you have made probes of large dressmakers pins or a similar item, you can back-probe the connector as well. Connect the meter probes to terminals 'A' and 'B' on the connector.

Turn on the ignition to read the TPS output voltage at the idle position. The reading should be 0.54VDC +/- 0.07VDC. The ideal is the center of the range, 0.54VDC for a stock engine. To adjust the output voltage, loosen the two Torx screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, the TPS sensor may be failing and could be a cause of stumbling and driveability problems.

After achieving the desired setting, turn off the ignition switch. Remove all jumpers or the scanner and reconnect the TPS connector as required.


Reinitializing the ECM

If you set a DTC during the procedure, the SES light should be illuminated on the dash. This ECM retains DTC data for the previous 50 engine starts, so the codes will eventually be cleared. If you want more immediate results, after shutting down the engine disconnect the negative battery terminal for five minutes. This will clear the ECM of all diagnostic trouble codes. Clearing the ECM also clears any data learned about your engine, and clears the radio presets. If you have a Delco-Loc or Theft Loc II radio, make sure you follow the procedure to unlock the radio protection before disconnecting the battery. This five minutes is also just about long enough to clean both battery cables. Reconnect the battery. When you first start the engine after clearing the ECM, the engine will operate with base parameters programmed into the ECM PROM. These parameters may not be optimum for your engine, but the ECM will enter a Block Learn Mode soon after the engine is warm and enters Closed Loop Mode. The ECM will write new data tables specific to your engine and will eventually rely on those tables instead of the base tables of the factory program. You can expedite this process by driving the car for 20 minutes under varying conditions to allow the ECM to initialize. Or you can wait and drive the car normally at your convenience. The BLM tables are constantly being updated as sensor input ranges change, but the greatest change will occur within the first twenty minutes of Closed Loop operation.

 

Holy smokes! What a detailed write up. Great job!

RACE ON!!!

 

Since you guys are talking about the IAC, I would like to chime in about my idle problem. I installed a brand new IAC when I got my 52mm throttle body from Dave. I forget his last name, as it has been about 9 months. Anyways, My car now idles at about 900 RPMs, which seemsa bit high to me. I did install FMS 24# injectors, a chip from Ski_dwn_it, and hooker headers and the rest of exhaust too. I did not see how to andjust pintle, so I did not bother, as I did not want to break the thing. PLEASE tell me if I did something wrong, and I need to make an adjustment. I want a lower idle. As always, Thanks guys.



Scott

 

You can't simply "adjust" it. It's in the chip. Check back with ski-dwn-it. Everything is new enough, I doubt you have a "hardware" problem. Does it have a fast cold idle? If so, the IAC is working.

RACE ON!!!