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Unread 09-08-2013, 08:29 PM   #1
foxcherokee
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00 Cherokee barely runs after warm-up

I have a 2000 4x4 Cherokee 4.0. I was having issues earlier with it stalling out while driving. I was told it was probably a voltage issue and after inspection I found the battery cables to be very corroded with only a few wires left intact. I replaced them and thought I had the issue resolved until I took it out tonight. Ran perfect for about 20 minutes(farther than it had before) then it all went south. I’m right back where I was…… the jeep will barely pull itself and consistently pops through the intake. I can put it in neutral and sometimes it will clear up, but as soon as I put back into drive it starts all over again. The only way I got it back to the house tonight was by throwing it neutral, shutting it off and restarting it. Once I did that it would pull itself through first gear but the minute it shifted to second it would begin cutting out again. It got so bad it kept dying roadside…. It starts right back up every time, but shortly after goes back to cutting out, popping through intake, etc.

Also, I took it by O’Reilly’s and they checked for codes but couldn’t find any. Check engine light is not on. HELP!!!!!

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Unread 09-09-2013, 05:29 AM   #2
tjwalker
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Backfiring through the intake (and your other symptoms) could indicate a lean fuel condition.

Job #1 is to verify your fuel pressure. If you don't have access to a fuel pressure gauge, they can be rented inexpensively at many parts stores (call around to see who does this.

For a 2000, you should see 49.2 psi, plus or minus 5 psi.

There certainly are many other possibilities, but with no check engine light, troubleshooting this is a "process of elimination" and fuel pressure is first on the list if this XJ were to be in my garage.

Good luck and keep us posted!
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Unread 09-09-2013, 05:43 AM   #3
foxcherokee
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I'll check this evening after work.
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Unread 09-09-2013, 11:25 AM   #4
CJ7-Tim
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As suggested check the fuel pressure. Test the Throttle Position Sensor. Also load test the battery.
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Unread 09-09-2013, 03:10 PM   #5
foxcherokee
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what kind of readout would I be looking for on the TPS? I'm assuming a 5 volt supply, but then what?
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Unread 09-09-2013, 04:43 PM   #6
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Ok.......I took my multimeter and hooked it to the ground of the TPS, then I took the other lead and placed it on the signal wire. I turned the ignition on, but didn't start the Jeep, and began opening the butterfly and found that I never got over 4 volts. would this be a sign of a faulty TPS? My reference wire has a solid 5 volts.
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Unread 09-09-2013, 05:32 PM   #7
CJ7-Tim
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TPS failure may have one or more of these Physical Symptoms:

1) The engine loses power and is stalling.

2) The engine will idle, but may die as soon as you press the gas pedal. Whendriving, it seems as if all power is gone.

3) Sometimes it feels as if the transmission is failed or isn't shiftingproperly, if at all. If you quickly jump on the gas you might be able to getthe transmission to shift, but it won’t shift properly by itself. Shiftingmanually, the transmission goes through all the gears.

NOTE: The throttle position sensor is also DIRECTLY involved with transmissionshifting characteristics. The TPS function should be verified early in thetroubleshooting process, when a transmission issue is suspected.

TPS TEST

The TPS is mounted on the throttle body. The TPS is a variable resistor thatprovides the Powertrain Control Module (PCM) with an input signal (voltage)that represents throttle blade position. The sensor is connected to thethrottle blade shaft. As the
position of the throttle blade changes, the resistance of the TPS changes.Along with inputs from other sensors, the PCM uses the TPS input to determinecurrent engine operating conditions. In response to engine operatingconditions, the PCM will adjust fuel injector pulse width and ignition timing.

The PCM supplies approximately 5 volts to the TPS. The TPS output voltage(input signal to the PCM) represents the throttle blade position. The PCMreceives an input signal voltage from the TPS. It is best to use an analogmeter (not digital) to see if the transition from idle to WOT is smooth with nodead spots. With your meter set for volts, put the black probe on a good groundlike your negative battery terminal. With the key on, engine not running, testwith the red probe of your meter (install a paper clip into the back of theplug of the TPS) to see which wire has the 5volts. This will vary in anapproximate range of from .25 volts at minimum throttle opening (idle), to 4.8volts at WOT wide open throttle.

Perform the test procedure again and wiggle and/or tap on the TPS while youwatch the meter. If you notice any flat spots or abrupt changes in the meterreadings, replace the TPS.

The TPS is sensitive to heat, moisture, and vibration, leading to the failureof some units. The sensor is a sealed unit and cannot be repaired onlyreplaced. A TPS may fail gradually leading to a number of symptoms which caninclude one or more of the following:

-Poor idle control: The TPS is used by the ECU to determine if the throttle isclosed and the car should be using the Idle Air Control Valve exclusively foridle control. A fault TPS sensor can confuse the ECU causing the idle to beerratic or "hunting".

- High Idle Speed: The TPS may report faulty values causing the engine idlespeed to be increased above normal. This is normally found in conjunction withaslow engine return to idle speed symptom.


Cheap crappy "Lifetime Warranty" parts are often out of specificationor even failed right out of the box. Many times they have a short service lifebefore they fail. Always buy top quality replacement parts and genuine Jeepsensors.

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Unread 09-09-2013, 08:02 PM   #8
foxcherokee
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one other thing.....I don't have the electric fan hooked up ( it went kapoot). could this be causing my problems? I have a clutch fan, so it's not overheating or anything. Also, I noticed a plug hanging by the oil filter that's not plugged in. I've searched buy an unable to locate where it goes. it's a single wire that's green in color I believe. any ideas?
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Unread 09-10-2013, 12:50 PM   #9
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update..... fuel pressure holds steady at 49psi. Any new ideas?
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Unread 09-10-2013, 05:05 PM   #10
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Test the TPS, then test the front O2 sensor.
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Unread 09-10-2013, 09:16 PM   #11
foxcherokee
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I posted the tps results earlier.... if you don't mind look back and tell me what you think on whether it's good or not. What's the best way to test the front o2?
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Unread 09-11-2013, 02:10 AM   #12
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I believe you can just unplug it and see if symptoms improve.

The engine defaults to the factory settings.

Check for a plugged exhaust too, I had a buddy that had a plugged exhaust and it would die whenever under load, ie: driving.

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Unread 09-11-2013, 04:35 PM   #13
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TPS needs 4.8 volts at wide open throttle.

O2 sensor testing is simple, use the Google, or see Youtube.
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Unread 09-11-2013, 06:17 PM   #14
foxcherokee
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Finally got it to act up while I had a fuel pressure gauge connected. When it began cutting out I noticed the fuel pressure had dropped to 20psi. Hopefully I'm getting closer to having this lined out. Next step is to drop the tank. I went ahead and put a new fuel relay in but it didn't make any difference. On a side note I found out the PO had let this thing set for nearly a year. I'm beginning to wonder it the tank liner has been eaten away and particles are randomly plugging the tank sock. Anyway, I'll keep ya posted. Thank you all for your replies.
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Unread 09-12-2013, 09:00 PM   #15
foxcherokee
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pulled tank and found it to be full of debris. The fuel pump was packed with brown murky gasoline..... sock was eaten away and full of debris. Really surprised it ran at all. The strange thing is when I had my gauge attached I hit the bypass several times and the fuel looked clean coming out. Took the pump housing apart and blew it out and thick muddy liquid came spurting out, too. I think I'll replace the entire assembly and be done with it.
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