How do you adjust a GM TBI?

How do you adjust a GM TBI?

Unplug the IAC valve located on the passenger side, rear of the throttle body. Start the engine. Insert a T-30 size Torx driver into the Idle adjustment screw that is located behind the plug removed earlier. Turn the screw to adjust the idle speed to 650 RPM +/- 50 RPM.

How do you reset TBI?

6- Start engine and run for 5 seconds, turn engine OFF and wait at least 30 seconds. This will reset the IAC control.

How do you test TBI IAC?

The easiest way to check to see if it is extending and retracting is to pull it out the IAC and hold the pintle (the cone shaped thing) with your thumb. Have someone power up the ECM it should extend then retract while keeping some pressure on the pintle (it will unscrew itself if you don’t do this).

What happens if idle air control valve is stuck open?

An obstructed or stuck-shut IAC will result in a rich air-fuel ratio at idle, so the engine will start very easily while cold and then die suddenly after a slight puff of black tail-pipe smoke. A stuck-open IAC might start fine while warm and may continue to run if the engine reaches high-enough RPM.

Why is TBI running rich?

IF you are running rich: Either your injectors are stuck open (usually an ECM fault), the fuel pressure is too high, or the ECM is getting incorrect signals from one of the sensors. If one of the sensors is bad, it is either the TPS, the O2 sensor or the MAP sensor. These sensors are what controls the fuel mixture.

How do you test IAC on a TBI?

How do you know if your throttle positioning sensor is bad?

1. An unexplainable bucking and jerking in the vehicle.
2. Sudden idle surges.
3. Sudden engine stalling without any apparent reason.
4. Hesitation while accelerating.
5. Sudden surges in speed while driving on the highway.
6. Intermittently flashing of check engine light for no apparent reason.
7. Difficulties in changing gears.

What causes a 350 TBI to run rich?

It’s easy to mix them up. IF you are running rich: Either your injectors are stuck open (usually an ECM fault), the fuel pressure is too high, or the ECM is getting incorrect signals from one of the sensors. If one of the sensors is bad, it is either the TPS, the O2 sensor or the MAP sensor.

How can I get more power out of my 5.7 TBI?

How to Get More Horsepower for the 1994 GMC 5.7 Liter TBI

1. Fill up your vehicle with high octane fuel rated above 90 octane.
2. Add fuel injector or carburetor cleaner to your vehicle’s gas tank every 3,000 miles.
3. Install a cold air intake on your vehicle’s air intake manifold.

What are the symptoms of a bad throttle positioning sensor?

• An unexplainable bucking and jerking in the vehicle.
• Sudden idle surges.
• Sudden engine stalling without any apparent reason.
• Hesitation while accelerating.
• Sudden surges in speed while driving on the highway.
• Intermittently flashing of check engine light for no apparent reason.
• Difficulties in changing gears.

What should TPS be at idle?

At idle is should be zero or a couple of degrees. Press down on the gas pedal very S-L-O-W-L-Y until the throttle is all the way open. If the TPS has a worn spot, most likely it will be between 0 and 20 percent throttle opening. Try holding the throttle between 0 and 20 percent to see if you get a steady reading.