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  #1  
Old March 19th, 2020, 07:15
baby ed baby ed is offline
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97 xj trouble

I have a 97 xj , 4.0, aw4, with approx 145k. My problem is, Jeep starts and runs perfect until the engine gets up to normal temp. Once warm, has a very rough idle, and very bad hesitation when accelerating. There is no cel. In the past week I've cleaned the throttle body, replaced the tps, cts, a new cap and rotor and cleaned up my grounds. Any suggestions?
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  #2  
Old March 19th, 2020, 07:21
OBEYXJ OBEYXJ is offline
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Re: 97 xj trouble

My 97 is the same way but my idle is intermittent. Have you checked your injectors are firing? and or have you read about unsticking your valves with mopar CCC or seafoam? Both these things have helped my idle.
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  #3  
Old March 19th, 2020, 07:54
CJR CJR is offline
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Re: 97 xj trouble

Hesitation after warm-up would seem to indicate a TPS problem with a thermal heat-soak and electrical resistance change problem. An acceleration "hesitation" can be either a " lean bog" or a "rich-bog" caused by the TPS sending an improper voltage signal to the computer. TPS are like accelerator pumps on carbs; i.e.bogs caused by either a high or low fuel pump-shots to the engine. If all of a sudden the computer leans or enriches the injectors, to cause a bog after warm-up, I'd suspect the TPS or its connections.

Best regards,

CJR
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  #4  
Old March 19th, 2020, 07:58
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Griffin Griffin is offline
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Re: 97 xj trouble

Don't forget to get new plugs and wires with your tuneup.

You can test your injectors by unplugging one at a time and feeling/listening for any difference in how the motor is running. Another method is to stick a long screwdriver onto the injector and put it up against your ear. It should make a constant clicking noise. If the clicking is irregular or if there's not clicking at all, the injector is bad. Here are some videos that hopefully help you.

https://youtu.be/tA_E6X4ISgQ
https://youtu.be/ZVXchvHefNc
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  #5  
Old March 19th, 2020, 08:14
baby ed baby ed is offline
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Re: 97 xj trouble

If it was a valve or injector, wouldn't it be that way cold too? I've done alot of searching and reading, and alot of people say when it's not up to operating temp, there's some sensors that aren't monitored. Any ideas on that?
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  #6  
Old March 19th, 2020, 08:45
RCP Phx RCP Phx is online now
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Re: 97 xj trouble

You can easily check with a scanner to determine of the PCM ever goes into closed loop vs being stuck in open loop.
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  #7  
Old March 19th, 2020, 10:09
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Tim_MN Tim_MN is offline
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Re: 97 xj trouble

145k is the end of Service Life for the O2 Sensors. The symptoms might make one suspect an O2 sensor fault as the engine management transitions to Closed Loop operation. In Open Loop operation most or all of the sensors are ignored and the PCM runs pre-programmed data.

A faulty injector would very likely cause a CEL Trouble Code, and sticky valves are not really a commonly seen problem. Injectors can be tested with a volts/ohms multi-meter and/or a Noid Light.
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Quote:
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Last edited by Tim_MN; March 19th, 2020 at 10:16.
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  #8  
Old March 19th, 2020, 10:58
baby ed baby ed is offline
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Re: 97 xj trouble

Thanks! I will look into all this when I get home
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  #9  
Old March 19th, 2020, 12:21
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8Mud 8Mud is offline
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Re: 97 xj trouble

Quote:
Originally Posted by Tim_MN View Post
145k is the end of Service Life for the O2 Sensors. The symptoms might make one suspect an O2 sensor fault as the engine management transitions to Closed Loop operation. In Open Loop operation most or all of the sensors are ignored and the PCM runs pre-programmed data.

A faulty injector would very likely cause a CEL Trouble Code, and sticky valves are not really a commonly seen problem. Injectors can be tested with a volts/ohms multi-meter and/or a Noid Light.
When My 96 did that it was the front O2 sensor. it was acting up for weeks, it never did pop a CEL until it was completely dead and I needed a tow home.
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  #10  
Old March 26th, 2020, 04:42
baby ed baby ed is offline
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Re: 97 xj trouble

Here's where I'm at. Watched the O2 sensor voltages on the scanner, everything seemed to toggle within range, and looked normal. Checked the map. 5v constant supply, 4.6 v at 0", 3.4v at 10", 2.2v at 15". The tps had 5v constant. 1.1v at 0 throttle, 4.1v at 100%. Any input on my findings?
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  #11  
Old March 26th, 2020, 07:13
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Re: 97 xj trouble

Quote:
Originally Posted by baby ed View Post

The tps had 5v constant. 1.1v at 0 throttle, 4.1v at 100%. Any input on my findings?



The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the 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. This will vary in an approximate range of from .25 volts at minimum throttle opening (idle), to 4.8 volts at WOT wide open throttle.

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.


Cheap crappy "Lifetime Warranty" parts are often out of specification or even failed right out of the box. Many times they have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep sensors.
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Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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  #12  
Old March 26th, 2020, 09:40
baby ed baby ed is offline
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Re: 97 xj trouble

Is the 1.1v at idle too much out of range?
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  #13  
Old March 26th, 2020, 10:25
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Re: 97 xj trouble

Yes. The 1.1 is too high and the 4.1 is too low.
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Quote:
Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.
Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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  #14  
Old March 27th, 2020, 04:58
baby ed baby ed is offline
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Re: 97 xj trouble

Well I swapped the tps with a known good 1. No change. Think I'm gonna set it on fire!!!
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  #15  
Old March 27th, 2020, 07:19
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Re: 97 xj trouble

Quote:
Originally Posted by baby ed View Post
Well I swapped the tps with a known good 1. No change.
Did you reboot the PCM adaptive memory ?



If your ODB-II Jeep had a weak or defective OBD engine sensor it is possible that there is a good deal a faulty data in the adaptive memory that should be deleted, and when replacing an OBD sensor you should at least consider rebooting the PCM.

This procedure will erase the 1996+ OBD-II “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed. After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics. Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn adaptive mode.

Disconnect the POSITIVE battery Terminal clamp and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory).

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”

The PCM Adaptive memory has now been flashed, or erased from the PCM. When you start the engine it will be running off a set of pre-programmed data tables that come with the PCM from the factory. When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”. The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.
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Quote:
Originally Posted by bimmerjeeper

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Quote:
Originally Posted by soyjer

Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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