RPM Low when Idle
Joined: Jun 2006
Posts: 501
Likes: 1
From: Philadelphia, PA
RPM Low when Idle
I have a 6 speed and recently on idle my RPM seems a bit low. I'm hitting 500RPM. The engine also seems to sputter sometimes when it's down to 500 RPM. Is this an issue with the transmission belt (i think?). Not sure what else it could be?
Anywhere I can start looking at in particular?
Thanks.
Anywhere I can start looking at in particular?
Thanks.
Joined: Mar 2009
Posts: 18,299
Likes: 1,488
From: By the sea, Tx
G35 sedan w/ too much money in mods
I would suggest cleaning your MAF and throttle body. Be careful with the TB, make sure you unplug the wire harness before you start.
Then reset the ECU and perform the idle air relearn process.
Then reset the ECU and perform the idle air relearn process.
Ok i found the instructions on how to do it right here
Basic ECU Reset
Operations Procedures:
1. Confirm that accelerator pedal is fully released, turn ignition switch “ON” (NOT start) and wait 3 seconds.
2. Repeat the following steps (2a and 2b) procedures quickly five times within 5 seconds.
2a. Fully depress the accelerator pedal (HARD).
2b. Fully release the accelerator pedal.
3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 10 seconds until the CEL starts blinking.
4. Fully release the accelerator pedal (while the CEL is still blinking)
5. Wait about 10 seconds.
6. Fully depress the accelerator pedal and keep it for more than 10 seconds.
7. Fully release the accelerator pedal (The CEL light will continue to blink).
8. Turn ignition switch to “OFF” position and now you can start the car. The CEL light should be gone. If the CEL light continues to remain ON, repeat the above steps. Remember, timing is EXTREMELY critical to resetting the ECU. You may even need someone's help to do this correctly.
Note: The following reset procedures are directly from the 2004 G35 Sedan Service Manual.
Accelerator Pedal Released Position Learning
Description:
Accelerator Pedal Released Position Learning is an operation to learn the fully released position of the accelerator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time harness connector of accelerator pedal position sensor or ECM is disconnected.
Operation Procedure:
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON and wait at least 2 seconds.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON and wait at least 2 seconds.
5. Turn ignition switch OFF and wait at least 10 seconds.
Throttle Valve Closed Position Learning
Description:
Throttle Valve Closed Position Learning is an operation to learn the fully closed position of the throttle valve by monitoring the throttle position sensor output signal. It must be performed each time harness connector of electric throttle control actuator or ECM is disconnected.
Operation Procedure:
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
Make sure that throttle valve moves during above 10 seconds by confirming the operating sound.
Idle Air Volume Learning
Description:
Idle Air Volume Learning is an operation to learn the idle air volume that keeps each engine within the specific range. It must be performed each time electric throttle control actuator or ECM is replaced, or if idle speed or ignition timing is out of specification.
Preparation:
Before performing Idle Air Volume Learning, make sure that all of the following conditions are satisfied. Learning will be cancelled if any of the following conditions are missed for even a moment.
- Battery voltage: More than 12.9V (At idle)
- Engine coolant temperature: 70 - 100 Degrees C (158 – 212 Degrees F)
- PNP switch: ON (Park/Neutral Position Safety Switch - AT only, MT fully depress clutch)
- Electric load switch: OFF (Air conditioner, rear window defogger, headlamps. Note: on vehicles equipped with daytime light systems, if the parking brake is applied before the engine is started, the headlamps will not be illuminated.)
- Steering wheel: Neutral (Straight-ahead position)
- Vehicle speed: Stopped
- Transmission: Warmed-up (For A/T models, drive vehicle for 10 minutes.)
Operation Procedure:
1. Perform "Accelerator Pedal Released Position Learning"
2. Perform "Throttle Valve Closed Position Learning"
3. Start engine and warm it up to normal operating temperature.
4. Check that all items listed under the topic PREPARATION (previously mentioned) are in good order.
5. Turn ignition switch OFF and wait at least 10 seconds.
6. Confirm that accelerator pedal is fully released, turn ignition switch ON and wait 3 seconds.
7. Repeat the following procedure quickly five times within 5 seconds:
7a. Fully depress the accelerator pedal.
7b. Fully release the accelerator pedal.
8. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 20 seconds until the MIL stops blinking and turned ON.
9. Fully release the accelerator pedal within 3 seconds after the MIL turned ON.
10. Start engine and let it idle.
11. Wait 20 seconds.
12. Rev up the engine two or three times and make sure that idle speed and ignition timing are within the specifications:
Idle speed A/T: 650rpm, + or - 50 rpm (in P or N position)
Idle speed M/T: 650rpm, + or - 50 rpm (in N position)
Ignition timing A/T: 15 Degrees BTDC, + or – 5 Degrees BTDC (in P or N position)
Ignition timing M/T: 15 Degrees BTDC, + or – 5 Degrees BTDC (in N position)
13. If idle speed and ignition timing are not within the specification, Idle Air Volume Learning will not be carried out successfully. If idle speed and ignition timing are within the specification and Idle Air Volume Learning cannot be performed successfully, find the cause of the incident by referring to the following Diagnostic Procedure:
1. Check that throttle valve is fully closed.
2. Check PCV valve operation.
3. Check that downstream of throttle valve is free from air leakage.
4. When the above three items check out OK, engine component parts and their installation condition are questionable.
5. If any of the following conditions occur after the engine has started, eliminate the cause of the incident and perform Idle Air Volume Learning all over again:
- Engine stalls.
- Erroneous idle.
Basic ECU Reset
Operations Procedures:
1. Confirm that accelerator pedal is fully released, turn ignition switch “ON” (NOT start) and wait 3 seconds.
2. Repeat the following steps (2a and 2b) procedures quickly five times within 5 seconds.
2a. Fully depress the accelerator pedal (HARD).
2b. Fully release the accelerator pedal.
3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 10 seconds until the CEL starts blinking.
4. Fully release the accelerator pedal (while the CEL is still blinking)
5. Wait about 10 seconds.
6. Fully depress the accelerator pedal and keep it for more than 10 seconds.
7. Fully release the accelerator pedal (The CEL light will continue to blink).
8. Turn ignition switch to “OFF” position and now you can start the car. The CEL light should be gone. If the CEL light continues to remain ON, repeat the above steps. Remember, timing is EXTREMELY critical to resetting the ECU. You may even need someone's help to do this correctly.
Note: The following reset procedures are directly from the 2004 G35 Sedan Service Manual.
Accelerator Pedal Released Position Learning
Description:
Accelerator Pedal Released Position Learning is an operation to learn the fully released position of the accelerator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time harness connector of accelerator pedal position sensor or ECM is disconnected.
Operation Procedure:
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON and wait at least 2 seconds.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON and wait at least 2 seconds.
5. Turn ignition switch OFF and wait at least 10 seconds.
Throttle Valve Closed Position Learning
Description:
Throttle Valve Closed Position Learning is an operation to learn the fully closed position of the throttle valve by monitoring the throttle position sensor output signal. It must be performed each time harness connector of electric throttle control actuator or ECM is disconnected.
Operation Procedure:
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
Make sure that throttle valve moves during above 10 seconds by confirming the operating sound.
Idle Air Volume Learning
Description:
Idle Air Volume Learning is an operation to learn the idle air volume that keeps each engine within the specific range. It must be performed each time electric throttle control actuator or ECM is replaced, or if idle speed or ignition timing is out of specification.
Preparation:
Before performing Idle Air Volume Learning, make sure that all of the following conditions are satisfied. Learning will be cancelled if any of the following conditions are missed for even a moment.
- Battery voltage: More than 12.9V (At idle)
- Engine coolant temperature: 70 - 100 Degrees C (158 – 212 Degrees F)
- PNP switch: ON (Park/Neutral Position Safety Switch - AT only, MT fully depress clutch)
- Electric load switch: OFF (Air conditioner, rear window defogger, headlamps. Note: on vehicles equipped with daytime light systems, if the parking brake is applied before the engine is started, the headlamps will not be illuminated.)
- Steering wheel: Neutral (Straight-ahead position)
- Vehicle speed: Stopped
- Transmission: Warmed-up (For A/T models, drive vehicle for 10 minutes.)
Operation Procedure:
1. Perform "Accelerator Pedal Released Position Learning"
2. Perform "Throttle Valve Closed Position Learning"
3. Start engine and warm it up to normal operating temperature.
4. Check that all items listed under the topic PREPARATION (previously mentioned) are in good order.
5. Turn ignition switch OFF and wait at least 10 seconds.
6. Confirm that accelerator pedal is fully released, turn ignition switch ON and wait 3 seconds.
7. Repeat the following procedure quickly five times within 5 seconds:
7a. Fully depress the accelerator pedal.
7b. Fully release the accelerator pedal.
8. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 20 seconds until the MIL stops blinking and turned ON.
9. Fully release the accelerator pedal within 3 seconds after the MIL turned ON.
10. Start engine and let it idle.
11. Wait 20 seconds.
12. Rev up the engine two or three times and make sure that idle speed and ignition timing are within the specifications:
Idle speed A/T: 650rpm, + or - 50 rpm (in P or N position)
Idle speed M/T: 650rpm, + or - 50 rpm (in N position)
Ignition timing A/T: 15 Degrees BTDC, + or – 5 Degrees BTDC (in P or N position)
Ignition timing M/T: 15 Degrees BTDC, + or – 5 Degrees BTDC (in N position)
13. If idle speed and ignition timing are not within the specification, Idle Air Volume Learning will not be carried out successfully. If idle speed and ignition timing are within the specification and Idle Air Volume Learning cannot be performed successfully, find the cause of the incident by referring to the following Diagnostic Procedure:
1. Check that throttle valve is fully closed.
2. Check PCV valve operation.
3. Check that downstream of throttle valve is free from air leakage.
4. When the above three items check out OK, engine component parts and their installation condition are questionable.
5. If any of the following conditions occur after the engine has started, eliminate the cause of the incident and perform Idle Air Volume Learning all over again:
- Engine stalls.
- Erroneous idle.
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Joined: May 2006
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From: Charlotte, NC and Central Virginia
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It depends if you disconnected the harness from your throttle body. Everytime I clean my throttle body I leave the harness connected. I don't have to worry about having to relearn the throttle valve close position
Registered User
Joined: Oct 2010
Posts: 11
Likes: 1
You might have clogged forward O2 sensors if your mileage is high. There is so little exhaust moving past them at idle, if they are getting clogged the response will be sluggish to correct the fuel mixture. Disconnect the large green connectors on each side of the engine near your coil packs, they will have two white wires (heaters) and a grey and black wire (signal). Then remove your O2's and wire brush the clogged metal shields if they are plugged.
ugh i have something like that too but its during my start... My car doesnt turn over when it should. Once I started it in the morning and it just turns right off. I had to do it twice before it started back up while I gave it some gas. Other than that, no problems. I love my car. 
