Durango stalls when cold
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Joined: Dec 2004
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Durango stalls when cold
My 99 Durango stalls (sometimes) when the engine is cold. This usually happens when I come to a stop. The engine starts and idles perfectly. I have changed the cap, rotor, wires and plugs. Did not slove the problem. There are no codes present at the OBD. Any ideas on where to go next?
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RE: Durango stalls when cold
ORIGINAL: robcox
It figures, the only reply I get is from a monkey.
It figures, the only reply I get is from a monkey.
Some advice: get your battery charged/tested. I'm not going to explain why/how, but it's a common problem with Dodge trucks. These magnum engines need a healthy battery to stay running, even though the battery has enough juice to start the motor again after it stalls. Very wierd indeed, but look into it. It's free. You are not the only one to experience this.
Thread Starter
Joined: Dec 2004
Posts: 4
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RE: Durango stalls when cold
Snipe, thanks for the advice. I did have a problem a year or two ago with a weak battery. I had to jump it early in the morning to get to work. The car would die as soon as I took the cables off. Anyway, I'll look into that. Thanks
Joined: Sep 2005
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RE: Durango stalls when cold
hey i am having similar prob with 01 durango 4.7 i have replaced battery and spark plugs and it did not help. mine starts fine in the morning but dies at idle. if iwait till later in the day, it starts and runs fine. the dealership says theres is no code on it and nothing wrong w/it, but it is still doing that. my husband thinks it is a moisture issue. i would love to hear how you were able to fix yours! (so i might have some pointers in the right direction.)
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Captain
Joined: Sep 2005
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From: Colorado
RE: Durango stalls when cold
The Idle Air Control Motor works with your Vehicle Speed Sensor to control idle speed during deceleration.
Coolant Temperature Sensor may be something else to consider as it controls the air/fuel mixture based on the collant temp.
Also check to see if the EGR valve is sticking open.
Description and Operation
IDLE AIR CONTROL (IAC) MOTOR - PCM OUTPUT
The IAC stepper motor is mounted to the throttle body, and regulates the amount of air bypassing the control of the throttle plate. As engine loads and ambient temperatures change, engine rpm changes. A pintle on the IAC stepper motor protrudes into a passage in the throttle body, controlling air flow through the passage. The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed.
At idle, engine speed can be increased by retracting the IAC motor pintle and allowing more air to pass through the port, or it can be decreased by restricting the passage with the pintle and diminishing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is moved (rotated) in steps, or increments. Opening the IAC opens an air passage around the throttle blade which increases RPM.
The PCM uses the IAC motor to control idle speed (along with timing) and to reach a desired MAP during decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of the wires are for 12 volts and ground to supply electrical current to the motor windings to operate the stepper motor in one direction. The other 2 wires are also for 12 volts and ground to supply electrical current to operate the stepper motor in the opposite direction.
To make the IAC go in the opposite direction, the PCM just reverses polarity on both windings. If only 1 wire is open, the IAC can only be moved 1 step (increment) in either direction, To keep the IAC motor in position when no movement is needed, the PCM will energize both windings at the same time. This locks the IAC motor in place.
In the IAC motor system, the PCM will count every step that the motor is moved. This allows the PCM to determine the motor pintle position. If the memory is cleared, the PCM no longer knows the position of the pintle. So at the first key ON, the PCM drives the IAC motor closed, regardless of where it was before. This zeros the counter. From this point the PCM will back out the IAC motor and keep track of its position again.
When engine rpm is above idle speed, the IAC is used for the following:
OFF-idle dashpot (throttle blade will close quickly but idle speed will not stop quickly)
Deceleration air flow control
A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
Power steering load control
The PCM can control polarity of the circuit to control direction of the stepper motor.
IAC Stepper Motor Program
The PCM is also equipped with a memory program that records the number of steps the IAC stepper motor most recently advanced to during a certain set of parameters. For example: The PCM was attempting to maintain a 1000 rpm target during a cold start-up cycle. The last recorded number of steps for that may have been 125. That value would be recorded in the memory cell so that the next time the PCM recognizes the identical conditions, the PCM recalls that 125 steps were required to maintain the target. This program allows for greater customer satisfaction due to greater control of engine idle.
Another function of the memory program, which occurs when the power steering switch (if equipped), or the A/C request circuit, requires that the IAC stepper motor control engine rpm, is the recording of the last targeted steps into the memory cell. The PCM can anticipate A/C compressor loads. This is accomplished by delaying compressor operation for approximately 0.5 seconds until the PCM moves the IAC stepper motor to the recorded steps that were loaded into the memory cell. Using this program helps eliminate idle-quality changes as loads change. Finally, the PCM incorporates a "No-Load" engine speed limiter of approximately 1800 - 2000 rpm , when it recognizes that the TPS is indicating an idle signal and IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechanically limit the position of the throttle body throttle plate. Never attempt to adjust the engine idle speed using this screw. All idle speed functions are controlled by the IAC motor through the PCM.
Coolant Temperature Sensor may be something else to consider as it controls the air/fuel mixture based on the collant temp.
Also check to see if the EGR valve is sticking open.
Description and Operation
IDLE AIR CONTROL (IAC) MOTOR - PCM OUTPUT
The IAC stepper motor is mounted to the throttle body, and regulates the amount of air bypassing the control of the throttle plate. As engine loads and ambient temperatures change, engine rpm changes. A pintle on the IAC stepper motor protrudes into a passage in the throttle body, controlling air flow through the passage. The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed.
At idle, engine speed can be increased by retracting the IAC motor pintle and allowing more air to pass through the port, or it can be decreased by restricting the passage with the pintle and diminishing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is moved (rotated) in steps, or increments. Opening the IAC opens an air passage around the throttle blade which increases RPM.
The PCM uses the IAC motor to control idle speed (along with timing) and to reach a desired MAP during decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of the wires are for 12 volts and ground to supply electrical current to the motor windings to operate the stepper motor in one direction. The other 2 wires are also for 12 volts and ground to supply electrical current to operate the stepper motor in the opposite direction.
To make the IAC go in the opposite direction, the PCM just reverses polarity on both windings. If only 1 wire is open, the IAC can only be moved 1 step (increment) in either direction, To keep the IAC motor in position when no movement is needed, the PCM will energize both windings at the same time. This locks the IAC motor in place.
In the IAC motor system, the PCM will count every step that the motor is moved. This allows the PCM to determine the motor pintle position. If the memory is cleared, the PCM no longer knows the position of the pintle. So at the first key ON, the PCM drives the IAC motor closed, regardless of where it was before. This zeros the counter. From this point the PCM will back out the IAC motor and keep track of its position again.
When engine rpm is above idle speed, the IAC is used for the following:
OFF-idle dashpot (throttle blade will close quickly but idle speed will not stop quickly)
Deceleration air flow control
A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
Power steering load control
The PCM can control polarity of the circuit to control direction of the stepper motor.
IAC Stepper Motor Program
The PCM is also equipped with a memory program that records the number of steps the IAC stepper motor most recently advanced to during a certain set of parameters. For example: The PCM was attempting to maintain a 1000 rpm target during a cold start-up cycle. The last recorded number of steps for that may have been 125. That value would be recorded in the memory cell so that the next time the PCM recognizes the identical conditions, the PCM recalls that 125 steps were required to maintain the target. This program allows for greater customer satisfaction due to greater control of engine idle.
Another function of the memory program, which occurs when the power steering switch (if equipped), or the A/C request circuit, requires that the IAC stepper motor control engine rpm, is the recording of the last targeted steps into the memory cell. The PCM can anticipate A/C compressor loads. This is accomplished by delaying compressor operation for approximately 0.5 seconds until the PCM moves the IAC stepper motor to the recorded steps that were loaded into the memory cell. Using this program helps eliminate idle-quality changes as loads change. Finally, the PCM incorporates a "No-Load" engine speed limiter of approximately 1800 - 2000 rpm , when it recognizes that the TPS is indicating an idle signal and IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechanically limit the position of the throttle body throttle plate. Never attempt to adjust the engine idle speed using this screw. All idle speed functions are controlled by the IAC motor through the PCM.
