engine rev
07-15-2007, 09:46 PM
#1
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engine rev
I've notice the last 4 or 5 days that when my car sits in the sun any length of time(or sits for and extended lenght of time, like over night) when I start it, my tach/engine rev gos alittle nuts. When I start it up, it bounces between 400/500rpm up to 1500/1600 rpms, for a few seconds(10-15 seconds) , but long enough for people to notice and annoy the hell out of me.
Anyone one else have this problem?
Anyone one else have this problem?
07-15-2007, 09:49 PM
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07-17-2007, 09:44 AM
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My guess:
Evap from the gas tank leaking into the intake.
Do you hear that knocking noise from the trunk or under the hood after you shut the car off and wait near it for about 2 to 3 min .I am pretty sure thats the car reliveing gas fumes(excess pressure from the gas tank)If that doesnt work properly it could make for erratic idle.
Found some info, could be one of these sensors,
Starting Mode
When the ignition is first turned ON, the control module energizes the fuel pump relay for 2 seconds. This allows the fuel pump to build pressure in the fuel system. The control module calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), mass air flow (MAF), and throttle position (TP) sensors. The system stays in starting mode until the engine speed reaches a predetermined RPM.
Run Mode
The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The control module ignores the signal from the heated oxygen sensor (HO2S). The control module calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), the mass air flow (MAF), and throttle position (TP) sensors. The system stays in Open Loop until meeting the following conditions:
• The HO2S has varying voltage output, showing that the HO2S is hot enough to operate properly.
• The ECT sensor is above a specified temperature.
• A specific amount of time has elapsed after starting the engine.
Specific values for the above conditions exist for this engine, and are stored in the electrically erasable programmable read-only memory (EEPROM). The system begins Closed Loop operation after reaching these values. In Closed Loop, the control module calculates the air/fuel ratio, injector ON time, based upon the signal from various sensors, but mainly from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.
Evap from the gas tank leaking into the intake.
Do you hear that knocking noise from the trunk or under the hood after you shut the car off and wait near it for about 2 to 3 min .I am pretty sure thats the car reliveing gas fumes(excess pressure from the gas tank)If that doesnt work properly it could make for erratic idle.
Found some info, could be one of these sensors,
Starting Mode
When the ignition is first turned ON, the control module energizes the fuel pump relay for 2 seconds. This allows the fuel pump to build pressure in the fuel system. The control module calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), mass air flow (MAF), and throttle position (TP) sensors. The system stays in starting mode until the engine speed reaches a predetermined RPM.
Run Mode
The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The control module ignores the signal from the heated oxygen sensor (HO2S). The control module calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), the mass air flow (MAF), and throttle position (TP) sensors. The system stays in Open Loop until meeting the following conditions:
• The HO2S has varying voltage output, showing that the HO2S is hot enough to operate properly.
• The ECT sensor is above a specified temperature.
• A specific amount of time has elapsed after starting the engine.
Specific values for the above conditions exist for this engine, and are stored in the electrically erasable programmable read-only memory (EEPROM). The system begins Closed Loop operation after reaching these values. In Closed Loop, the control module calculates the air/fuel ratio, injector ON time, based upon the signal from various sensors, but mainly from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.
Last edited by Coblasts; 07-17-2007 at 10:46 AM.
07-25-2007, 09:12 PM
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Could be a problem with throttle positioning sensor. Mine started doing that stuff as u all described but now its worse. It does it every time I slow down for a light or to park. If my AC is on it will sometimes just die. Still looking into this but pretty sure its tps sensor. Problem is it cant be replaced without changing out entire throttle body.
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