Rough idle and shuts off

Tiny
SWAGGER82
  • MEMBER
  • 1993 CHEVROLET 1500
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Truck starts and idles perfectly fine as long as wheel is maxed out to the left or right anywhere else it spits and sputters and quits running.
Saturday, April 27th, 2019 AT 11:32 AM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Welcome to 2CarPros.

It sounds like not enough air is getting to the engine at idle. There is a component called an idle air control valve. It basically allows air to enter the engine when at an idle. I have a feeling that is the issue or the throttle body needs cleaned.

First, here is a link that explains how to check a throttle body. Try this first.

https://www.2carpros.com/articles/throttle-actuator-service

If that doesn't help, then I need you to remove the idle air control valve (IAC). I am going to provide the directions for replacement of the IAC. However, before you replace it, confirm that both the pintle valve on it and where it enters the throttle body are clean and free of carbon or dirt. That is the only place air enters when the throttle plate is closed.

Here are the directions. The attached pics correlate with the directions.

IDLE AIR CONTROL (IAC) VALVE REPLACEMENT
IAC Thread Mounted 10mm Pintle

picture 1

NOTES:
The Idle Air Control (IAC) valve is an electrical component and must not be soaked in any liquid cleaner or solvent. Otherwise damage could result.
The IAC valve for this application is thread-mounted and has a dual taper, 10 mm diameter, pintle. Any replacement of the IAC valve must have the correct part number, with the appropriate pintle taper and diameter for proper seating of the valve in the throttle body.

REMOVE OR DISCONNECT
1. Disconnect electrical connector.
2. Remove IAC valve, use a 32 mm (1 1/4") wrench.
3. Remove IAC gasket and discard.
4. Clean old gasket material from surface of throttle body assembly to insure seal of new gasket.

CLEAN
Both original and replacement IAC valves have a special factory applied thread-locking compound applied to the screw threads. If the valve removed from throttle body is being reinstalled, DO NOT remove thread-locking that may remain on the threads.
Clean IAC valve seating surfaces on throttle body to assure proper seal of new gasket and IAC valve.

Idle Air Control Valve Pintle Retraction (Manually)

picture 2

NOTES:
If the IAC valve was removed during service, its operation may be tested electrically with the IAC/ISC Motor Tester (J-37027 or BT-8256K) or equivalent. Before installing a IAC valve, measure the distance between the tip of the valve pintle and the mounting surface. If the dimension is greater than 28.0 mm (1.10 inches), the valve pintle must be retracted to prevent damage to the valve. This may be done electrically using an IAC/ISC Motor Tester or manually by exerting firm pressure, as shown in the illustration, with a slight side to side movement on valve pintle to retract it.
No physical adjustment of the IAC valve assembly is required after installation. The IAC valve pintle is reset by turning the ignition ON for ten seconds and then OFF. The ECM then resets the pintle to the correct position. Proper idle regulation should result.

INSTALL OR DISCONNECT
1. Install the IAC valve into throttle body with new gasket.

NOTE: New IAC valves have been reset at the factory and should be installed in the throttle body in an "as is" condition, without any adjustment.

2. Tighten IAC valve assembly to 18.0 Nm (13.0 lb-ft).
3. Reconnect electrical connector to IAC valve.
4. "START" engine and allow it to reach operating temperature.

_______________________________________

Let me know if this helps or if you have other questions.

Take care,
Joe

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Saturday, April 27th, 2019 AT 10:09 PM
Tiny
SWAGGER82
  • MEMBER
  • 2 POSTS
I'm not new to turning wrenches. But could you explain why the iIAC would let it run fine if wheel is turned all the way to the left or right and no where in between.
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Sunday, April 28th, 2019 AT 9:36 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Not a problem. When an extra load is placed on the engine (PS / AC) the computer steps the RPM's up to prevent stalling or extremely low idle. The IAC is all part of the system.
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Sunday, April 28th, 2019 AT 4:46 PM

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