A smith gs 100 302 Cranks and runs full throttle with air valve open. But if you close the air valve, the motor shuts off

no ca/truckr model told at all, of many 3 or 4.
no engine told and is and engine problem.

the VIN digit #8 is the engine code

NO model told.
ram 1500 ?, 2500, 3500 or 4000 , and not the Ram van. 1998 (4000 Mexico or Canada)
no engine told one is Diesel;,
3.9 L Magnum V6
5.2 L Magnum V8
5.9 L Magnum V8
5.9 L Cummins turbo-diesel I6<<< ill not cover this ever.
8.0 L Magnum V10

does the starter motor always work correctly every time, called cranking?

we get the fact it does not start. sometimes
but what is not clear, at all, is that the starter always makes this sound called cranking? or fails to do cranking

see MP3 post

It could be a dirty throttle body, clogged fuel filter or a bad throttle positioning sensor. Also check the ECM to see if it is setting any useful diagnostic codes.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/dave_fb2c45146b845cea

Usually when the engine is "hunting" for the idle speed, the throttle position sensor or idle air control valve is faulty, or there is gunk in the throttle body, or a vac leak somewhere.
The computer controls the idle speed by using that control valve.
Is the check engine light on when the engine is running ?

These are all things that can affect your gas mileage and engine performance.

To check for vacuum leak, look for unhooked hoses on top of engine. If OK, use starter fluid and spray along intake manifold gaskets with engine running. If engine speeds up, there is a leaking gasket.

IAC deals with idle. Does the car idle smoothly? If not, remove IAC to see if it's dirty. I will paste instructions below for the IAC valve.

Throttle body dirty--what code is this? never heard of such a code, but you can clean the throttle body wioth carb cleaner. I will paste instructions below.

IAC valve info:

Operation The amount of air taken in during idling is regulated by the opening and closing of the servo valve located in the air passage that bypasses the throttle valve. The servo valve is opened or closed by the activation of the stepper motor (incorporated within the idle air control motor in the forward or reverse direction. Battery positive voltage is supplied, by way of the MFI relay, to the coil of the stepper motor. The engine control module switches ON the power transistors (located within the engine control module) in sequential order, and, when current flows to the stepper motor coil, the stepper motor is activated in the forward or reverse direction.

Removal & Installation

1. Disconnect the negative battery cable.
2. Detach the electrical connector at the sensor.
3. Remove the sensor from the throttle body.
   

To install:

1. Install the sensor in the opening in the throttle body and tighten the sensor.
2. Attach the electrical connector to the sensor.
3. Connect the negative battery cable.

Testing
Checking Coil Resistance

1. Disconnect the idle air control motor connector and connect the jumper (test harness).
2. Measure the resistance between terminal (2) of the connector at the idle air control motor side and terminal (1) or terminal (3). Standard value: 28-33 ohms at 68°F
3. Measure the resistance between terminal (5) of the connector at the idle air control motor side and terminal (6) or terminal (4). Standard value: 28-33 ohms at 68°F
4. If not within specifications, replace the IAC Valve.
5. If within specifications, check connectors and wiring between the sensor and ECM/PCM.
   

Checking Operation Sound

1. Check that the operating sound of the stepper motor can be heard over the idle air control motor when the ignition switch is turned to the ON position (without starting the engine).
2. If no operating sound can be heard, check the stepper motor drive circuit. (If the circuit is good, a defective stepper motor or engine control module is suspected.)

IAC picture--mounted on top side of engine.

Throttle body--loosten clamp to right of throttle body and pull hose off. Use electric parts cleaner or carb cleaner--spray on dirt with engine running. don't touch any sensors inside throttle body--sensors are delicate.

Have you looked at your idle air control valve What is it? This is an electrically driven valve that allows additional control over the throttle at idle Where is it located? The IAC is located on or adjacent to the throttle body and consists of a small device held on by two bolts with an electrical connector.
How does it work? When the throttle is closed the throttle plate closes off any air from the intake manifold. In order to stop the engine from stalling due to lack of air the IAC opens a small valve allowing air to pass from the air ducting to the intake manifold. Often the IAC components consist of an air inlet port in the inside wall of the throttle body, immediately in front of the throttle plate, with a similar exit port behind the throttle plate. Connecting the two ports is a motor driven valve. When the valve is opened air effectively by-passes the closed throttle plate to maintain the engine at idle. The IAC also augments the throttle when additional power demands are put on the engine such as steering.


Symptoms of faulty IAC

• Poor starting: If the IAC fails to open or the inlet/exit ports are clogged shut with carbon the engine may start and then promptly stall. The engine can be kept running by pressing the accelerator. However any additional demand on the engine such as power steering or putting the car into drive (automatic) will cause the engine to stumble badly and often stall.
• Engine cut out: Even with the engine warmed when the vehicle is stationary such as at a red light the putting of the transmission into of 'drive' to pull away before the accelerator is pressed can cause the engine to stall. (Note this differs from the TPS fault which causes engine stall due to the accelerator being pressed too quickly)

How to check? Physically remove the IAC but keep the electrical connection to it. Temporarily block off the now open ports on the throttle, turn the engine on and examine the IAC valve action in response to additional loads (power steering inputs etc). The valve should open and close according to demand.

How to fix? If the motor of the IAC has failed then replace the IAC. If the valve is gummed closed by baked oil and carbon then clean it thoroughly with carburetor choke cleaner spray and a cloth. Similarly if the entry and exit ports on the throttle body to the IAC look blocked again clean them out thoroughly.

I have the same problem with my 2001 escape V6. there is a really cheap temporaly fix....actually it could be permanent and will never damage your vehicule. When u open the hood there is a plastic guard with the ford logo and engine size that is held in place with 3 bolts, 1 on the left 2 on the rigth. Unscrew these and the guarding comes off. Once this remove you will see the accelarator pedal cable hook to the throttle. U can rock the throttle manually to give more gaz when your motor is running. At the bottom of the throttle there is a small screw that is not touching to anything, if u screw it a couple of turn it will start pushing on the throttle and stop your vehicule from stalling. Adjust this screw until your RPM indicator on your dash board is at around 600 rpm wich is the normal idle speed of your motor when functionning normaly. The real problem is an air intake valve that is defective (150$) because it open when the vehicule starts but shut because defective causing your engine to stall because no air for combustion....By forcing the screw on the throttle the valve cannot shut down and that is why your vehicule wont stall........It takes a full 5 minutes to do the mechanical screw fix...And I drove one year on it before replacing the valve........good luck from a friendly canadian........

This is proplem with the IAC valve , try clean the valve and if that doesnt work replace it.

An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body

Thanks
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Smith

I would say idle air control valve sticking. its common on Renaults. This valve controls the air passing through the throttle body when you open and shut throttle. eg, foot down throttle open, the idle valve will be shut. back off throttle, then the air is shut off through main throttle body, so the valve opens to allow just enough air in for tickover. if valve sticking or moving to slowly it will not open in time to catch the idle when throttle shut, hence it cuts out.

TL

I wanted to start a thread specifically about failures within the throttle body concerning the GS300 (1998 in my case)

My symptons were:
VSC, VSC OFF, and ENGINE Lights would come on, followed by my car going into Limp Mode, where only that last 25% (if that) of the throttle would respond (basically have to floor the pedal to even move at all).

During the mornings, or when the engine was COLD, the throttle operated normal...then once the car warmed up, usually at about 10 mins, the problem would start...it happened intermitantly at first...1 or 2 days over the course of a week, then it became more consitent, until last week it became a daily problem.

The first part I tried was the Throttle Position sensor, which is on the front side of the throttle body, and the easiest thing to replace...this didnt help at all. $300 part from Lexus, $80 part from RockAuto.com (exacly same part toyota OEM)

THE PART THAT FIXED THE PROBLEM:
===========================================
"Idle Valve Motor", which is the larger electrical object next to the TPS on my 98 GS300. Problem is solved.

The Codes I got were P1120 and P1121 - Accelerator Sensor problem. However it wasnt really the Accelerator Sensor, it was indeed to actual electrical Motor that controls the opening of the Butterfly valve inside the Throttle body.

I found the problem by good old trouble shooting, and using an ohm meter to see if the throttle electric motor was getting elev, I found that the elec motor just to the left of the TPS was basically freaking out and shutting down. The Accelerator Pedal Sensor is on the Back-side of the throttle body where the throttle cable connects to, and has a spring on it. It was fine.

GS300's are indeed "drive by wire" concerning the throttle...the cable triggers the Accel Pedal Sensor, which sends a signal to the ECU, the ECU then sends power to the Idel Valve Elec Motor (next to the TPS), which opens and closes the mechanical butterfly valve, then the TPS sensor detects how far the elec motor is actually opening the butterfly valve...its a closed-loop feed-back system, meaning any failure in any sensor will cause the entire systm to fail.

The throttle cable apparently is ONLY there to allow the fail-safe of having that last 10-25% throttle when the electronic system fails...there is a gearbox inside the throtle body which allows the tail end of the throttle to manually engage the butterfly valve...the rest of the time, the butterfly valve is 100% opened and closed via the idle control motor.