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**mQb0aVZe** · 09-12-2010, 05:43 AM

1989 w. the 4.0L Automatic.

It only does this while the engine is cold. Turns on fine. idles fine. Give it gas its fine. But this is where it almost stalls out every time.

Give it gas, it revs up. Left off gas and give it gas again, it almost stalls out every time, but then revs up before it dies. Only will do this a couple of times, only while it is cold.
I just replaced the EGR thinking that it could be the issue. I had the vacuum line unplugged because if it was plugged into it, it would stall out if you were not giving it any gas no matter the speed. So had to replace that for safety + emissions and was hoping that it would fix the cold almost stalling out issue it has atm but it did not.

Clean the IAC stepper motor and passages.

The IAC should be on the throttle body, it controls the throttle blades for idle control. It may not be reacting fast enough when coming down, if its lazy it won't react fast enough to keep the engine idling. When cold the motor will be slower than when warm.

You can remove the motor and spray the pintle with carb cleaner, you can also spray it into the passage to get rid of gunk and carbon build up which might be impeading the motor.

If that doesn't fix it the issue is something else, or the motor is bad. But the only way to truly diagnose a bad stepper motor is to look at the IAC counts using a scan tool.

09-12-2010, 05:43 AM	#8
mQb0aVZe Join Date Nov 2005 Posts 425 Senior Member	1989 w. the 4.0L Automatic. It only does this while the engine is cold. Turns on fine. idles fine. Give it gas its fine. But this is where it almost stalls out every time. Give it gas, it revs up. Left off gas and give it gas again, it almost stalls out every time, but then revs up before it dies. Only will do this a couple of times, only while it is cold. I just replaced the EGR thinking that it could be the issue. I had the vacuum line unplugged because if it was plugged into it, it would stall out if you were not giving it any gas no matter the speed. So had to replace that for safety + emissions and was hoping that it would fix the cold almost stalling out issue it has atm but it did not. Clean the IAC stepper motor and passages. The IAC should be on the throttle body, it controls the throttle blades for idle control. It may not be reacting fast enough when coming down, if its lazy it won't react fast enough to keep the engine idling. When cold the motor will be slower than when warm. You can remove the motor and spray the pintle with carb cleaner, you can also spray it into the passage to get rid of gunk and carbon build up which might be impeading the motor. If that doesn't fix it the issue is something else, or the motor is bad. But the only way to truly diagnose a bad stepper motor is to look at the IAC counts using a scan tool.
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