Random high idle
09-01-2014, 03:46 AM
#1
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Model: Cherokee
Random high idle
Hey. So sometimes while driving she wants to take off... It goes into high idle ~1500 rpm for a few seconds then it drops back down, this often happens at stop lights, stop signs, in parking lots, especially while in neutral or park (then it will really try to take off) oh and when I first start it revs high then slowly drops down....
Thoughts are.....
throttle position sensor?
Fuel problem?
Air fuel?
Homicidal feelings towards me?
Suicidal feelings for itself?
Thoughts and ideas welcome, if I can't fix it it's going to the dealer..well because I can't have a vehicle that wants to drive off when I dont want it to...
Thoughts are.....
throttle position sensor?
Fuel problem?
Air fuel?
Homicidal feelings towards me?
Suicidal feelings for itself?
Thoughts and ideas welcome, if I can't fix it it's going to the dealer..well because I can't have a vehicle that wants to drive off when I dont want it to...
09-01-2014, 04:17 AM
#2
CF Veteran
1) clean IAC
2) Clean throttle body and valve
3) test TPS
4) check for vacuum leaks around intake
Hold on the feelings part for now.
See how this goes.
2) Clean throttle body and valve
3) test TPS
4) check for vacuum leaks around intake
Hold on the feelings part for now.
See how this goes.
09-01-2014, 09:26 AM
#3
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Hey. So sometimes while driving she wants to take off... It goes into high idle ~1500 rpm for a few seconds then it drops back down, this often happens at stop lights, stop signs, in parking lots, especially while in neutral or park (then it will really try to take off) oh and when I first start it revs high then slowly drops down....
Thoughts are.....
throttle position sensor?
Fuel problem?
Air fuel?
Homicidal feelings towards me?
Suicidal feelings for itself?
Thoughts and ideas welcome, if I can't fix it it's going to the dealer..well because I can't have a vehicle that wants to drive off when I dont want it to...
Thoughts are.....
throttle position sensor?
Fuel problem?
Air fuel?
Homicidal feelings towards me?
Suicidal feelings for itself?
Thoughts and ideas welcome, if I can't fix it it's going to the dealer..well because I can't have a vehicle that wants to drive off when I dont want it to...
But, I want to know what the hell it is that you're driving.
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09-01-2014, 02:31 PM
#9
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
09-01-2014, 02:50 PM
#11
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Friggin "smart" phones.........
09-01-2014, 02:56 PM
#12
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I'm embarrassed since Cruiser54 is going to see my response LOL... But I had idle issues, and shifting issues. Been diagnosing and wrenching for a while now. Went with the ol GUT feeling.. 
and I was right.
BUT!!! I Recommend!! (Pulled from another Forum from a member named CJ7-Tim using Google
)
TPS TEST
You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.
Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.
The TPS is sensitive to heat, moisture, and vibration, leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following:
-Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
- High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
-Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
-Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
- Engine Misfire: A faulty TPS can report values outside the acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessive misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.
and I was right.BUT!!! I Recommend!! (Pulled from another Forum from a member named CJ7-Tim using Google
)TPS TEST
You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.
Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.
The TPS is sensitive to heat, moisture, and vibration, leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following:
-Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
- High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
-Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
-Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
- Engine Misfire: A faulty TPS can report values outside the acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessive misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.
09-01-2014, 03:03 PM
#14
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Model: Cherokee