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Unread 06-22-2013, 08:29 PM   #16
tjwalker
It's the crank sensor!
 
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The "throttle position sensor" is still in play. It provides critical input signals to control the AW4 transmission. Here's more.
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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.

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Unread 06-22-2013, 08:36 PM   #17
skyway0018746
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^^ that's a lot of stuff! But my experience with bad tps is that the same thing happens all the time ( cold, warm, hot.)
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Unread 06-23-2013, 01:51 AM   #18
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Thanks but the TPS was one of the first things I changed and it made no difference with my shifting problem. I'll grab a voltmeter and check it out just to be sure.
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Unread 06-24-2013, 02:12 AM   #19
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I swapped the TCM over but still have the same problem. Checked the TPS and it had 5 volts going into it. At idle the TPS output voltage was 0.87 volts and at wide open throttle it was 3.8 volts.

I might try some of this stuff next:

http://www.nulon.com.au/products/Spe.../#.UcfvcNg7tx0
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Unread 06-24-2013, 08:49 AM   #20
Pats94
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Quote:
Originally Posted by O-D View Post
I swapped the TCM over but still have the same problem. Checked the TPS and it had 5 volts going into it. At idle the TPS output voltage was 0.87 volts and at wide open throttle it was 3.8 volts.

I might try some of this stuff next:

http://www.nulon.com.au/products/Spe.../#.UcfvcNg7tx0
Don't waste the money. There is no fix in a can.
You say it will manually shift? Then snake oil won't fix it.
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Unread 06-24-2013, 05:10 PM   #21
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Originally Posted by O-D View Post
No change with the kickdown cable adjusted. I pulled the TCM fuse and manually shifted through the gears with no problems, and this was still while it was cold.
If it manually shifts my guess is a sensor or wiring. Somehow heating is closing a contact of some sort in the electrical side allowing the solenoid for the 1-2 to function. You've changed the TCM out with a known good one and right year?
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Unread 06-24-2013, 05:30 PM   #22
skyway0018746
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What happens if the Jeep is warmed up before putting it in drive?
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Unread 06-25-2013, 02:44 AM   #23
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Quote:
Originally Posted by Pats94 View Post
If it manually shifts my guess is a sensor or wiring. Somehow heating is closing a contact of some sort in the electrical side allowing the solenoid for the 1-2 to function. You've changed the TCM out with a known good one and right year?
I'll pull the TCM fuse out again next time it's cold and confirm the manual shifts. Yes it is a good working TCM out of the same year model.

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What happens if the Jeep is warmed up before putting it in drive?
I did this once and it shifted fine but I'll try this again to be sure.
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Unread 06-25-2013, 02:48 AM   #24
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Quote:
Originally Posted by Pats94 View Post
You say it will manually shift? Then snake oil won't fix it.
Quote:
Originally Posted by Pats94 View Post
If it manually shifts my guess is a sensor or wiring.
I take it from these responses that if it manually shifts OK then it rules out things like a sticky valve in the valve body or the pump on its way out?
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Unread 06-25-2013, 06:23 AM   #25
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Quote:
Originally Posted by O-D View Post

I take it from these responses that if it manually shifts OK then it rules out things like a sticky valve in the valve body or the pump on its way out?
Yup. Its the electronics that tell it to shift.
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Unread 06-28-2013, 08:34 PM   #26
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Quote:
Originally Posted by tjwalker View Post
The "throttle position sensor" is still in play.
Quote:
Originally Posted by Pats94 View Post
Yup. Its the electronics that tell it to shift.
You guys were right. I changed the TPS again (despite already replacing it) and my transmission is now shifting smoothly again when cold. Thanks!

I'm not happy with the Standard brand of TPS I got from RockAuto. It was the second one they've sent out to me because the previous one was faulty too...different symptoms though - it didn't affect the transmission last time. This is what the TPS looked like, it fell apart in my hands when I unplugged it:



My troubles aren't completely over yet. Sorry to hijack this thread but I think the TPS was only part of the problem because I still have a lack of acceleration in other gears when cold. I can put my foot down and there's no increase in speed, the revs stay constant and it feels like the engine isn't getting enough fuel. I've got dual fuel installed (LPG) so I can rule out things like the fuel pump etc.

What other sensors could cause a lack of power/acceleration when cold? I don't think it's the O2 sensor because I've replaced that too but I guess that doesn't mean much. What about the MAP sensor?
Quote:
Originally Posted by tjwalker View Post
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.
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Unread 06-28-2013, 10:27 PM   #27
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Good to hear you have one problem down. Could be the map, I don't have experience with the map sensor ( yet) or lpg
Sounds like it could be the map from your quote. Or maybe the iac since you say its not getting enough fuel. What year is the Jeep?
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Unread 06-29-2013, 02:17 AM   #28
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It's a 1996 XJ (RHD).
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Unread 06-29-2013, 09:08 AM   #29
skyway0018746
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I would say the map sensor is next on the list. How are the cap / rotor and plugs?
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Unread 06-29-2013, 08:21 PM   #30
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My cap, rotor and plugs are regularly changed but I could swap them over if I run out of other things to try. I checked all the sensors with a multimeter (including the MAP) and all show the correct volts/ohms. The only one I didn't get to yet was the upstream O2 sensor but I might unplug it altogether and see if the problem goes away with it disconnected.
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