keeps Shutting off
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Here's the writeup for ya, give it a spin when you get the chance.
Originally Posted by tjwalker
The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad
You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is 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. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.
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: -
NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!
• 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 fault TPS can report values outside the denied 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 excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.
You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is 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. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.
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: -
NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!
• 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 fault TPS can report values outside the denied 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 excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.
Last edited by salad; Jan 1, 2014 at 09:27 PM.
Thread Starter
Junior Member
Joined: Feb 2013
Posts: 74
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So I called the garage this morning. they said the only code it had was the intake air temp sensor.. He told me he was going to replace that, the distributor cap and rotor (since I already put plugs and wires on it) and he also wanted to replace the fuel pump relay and pick up assembly.. I understand it sux that I'm not AT ALL involved in this at the moment. I just want to keep anyone that wants to lend an option in the loop.. Also I just remembered the first time I took it to the other garage.. It had a code for the fuel pump resistor bypass relay.. Would that be that same thing thus guy is talking about?
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Interesting. While it's like that the IAT is off that won't cause shutting off. Dist cap and rotor will cause poor running sure, I'm surprised they weren't done already.
1995 doesn't have a fuel pump ballast resistor... I'm not intimately familiar with the OBD-I Jeeps but I'm like 90% sure the pump is powered by a relay when you turn the key to RUN and that's it.
1995 doesn't have a fuel pump ballast resistor... I'm not intimately familiar with the OBD-I Jeeps but I'm like 90% sure the pump is powered by a relay when you turn the key to RUN and that's it.
Thread Starter
Junior Member
Joined: Feb 2013
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They just started on it this morning.. A buddy of mine worked atThe first garage and I was there when he hooked up the diagnostic machine and that's what it said the code was.. But when he looked it up on the computer.. It didn't have that code.. So from there I have no idea.. All he did after that was switch the fuel pump relay with another relay matched the pins.. But like I said before.. I'm useless with that stuff..
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
TPS wouldn't surprise me, but a good one costs a few bucks. BWD TPSes are unfortunately very unreliable, like most other aftermarket engine management sensors. Make sure to test it first, and if it's bad invest in a quality Mopar unit.
You can test the MAP if you like but they don't really go bad very often. Turns out I have a few pages from the '95 XJ FSM, here's a test procedure for the MAP:
You can test the MAP if you like but they don't really go bad very often. Turns out I have a few pages from the '95 XJ FSM, here's a test procedure for the MAP:
Thread Starter
Junior Member
Joined: Feb 2013
Posts: 74
Likes: 0
So The garage called back today.. They said they drive it around Friday and it shut of so much they almost just towed it back. They said they got a TPS and coil from another motor. Drove it around for 3 days and it hasn't shut off since. I'll pick it up tmw and drive it all week.. Hopefully everything is good now.. I'll update the thread next week.. Maybe this thread will help someone else.. Just wish I could've worked on it myself.
CF Veteran
Joined: Jan 2012
Posts: 3,170
Likes: 312
From: Australia
Year: 1997 (RHD)
Model: Cherokee (XJ)
Engine: 4.0 ltr
"....and so the story ends, of the new kid in town, who got himself into a somewhat rough start, but due to the calming effect of the elders, saw himself taken up into the family of XJ land...."
Just reading through this thread, I couldn't help myself...
Happy New Year from across the Big Pond.
Just reading through this thread, I couldn't help myself...
Happy New Year from across the Big Pond.
Last edited by Roler; Jan 7, 2014 at 12:32 PM.
CF Veteran
Joined: Jul 2012
Posts: 1,395
Likes: 1
From: SD
Year: 1998
Model: Cherokee
Engine: 4.0
CF Veteran
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
But if it doesn't STAY fixed, has anybody considered the fact that he ran the tank dry, and THEN started having this problem? And one of the fixes thrown at it was to replace a fuel filter that was "so rusted it had a hole in it".
Hmmm.
I'd throw a fuel pressure test at that thing if it acts up again.
With Canadian bacon on it!
Thread Starter
Junior Member
Joined: Feb 2013
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That's what I originally thought.. Cause it was fine until i ran it dry..But it still shut off after the fuel filter was replaced. There can't be much else left.. I'm just glad someone other then me got to see it shut off.. Its so annoying when I have a problem that vanishes when someone else drives it
CF Veteran
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
I was thinking that some crud got through that rusted filter and is creating problems elsewhere. If that's the case, replacing the filter, while necessary, would not solve this problem.