Question about 2000 Jeep Grand Cherokee

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PO171 OBD-II Trouble Code " System Lean To Bank 1

I have a 2000 Jeep Grand Cherokee. Engine rough at Idle and exhibits lack of power and stumbles at about 45 mph.

Scanner Freeze Rame Data ( At Idle )

RPM: 832
Load % : 16
Coolent Temp: 114
ST FTRM1( % ): 26.5
LT FTRM1 ( % ): 32.0
ST FTRM3:( % ): -2.2
LT FTRM3 ( % ) : -52.2
Fuel System: Closed

Replaced fuel filter/regulator, replace 02 sensors, replaced vacuum hoses and fittings, incl. EGR fittings at valve conver. Replaced IAT sensor. Checked MAP sensor, throttle position sensor and idle sensor voltages with VOM meter - all OK. Checked fuel perssure - OK. Removed and cleaned throttle body. Removed and cleaned spark plugs. Should I be focusing on fuel related problem or vacuum related problem. Change fuel injectors ? I'm beginning to suspect water in fuel. I would appreciate your help.

Jim Colman

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  • Tarzan14 Jan 06, 2009

    Engine Check light on, Runs ruff, Code shows PO171. 1998 Jeep Cherokee. Need to know what is actually wrong with the vehicle.

  • nyxt00 May 11, 2010

    If you think its water in the lines you can try adding HEET to the tank. You can also try a fuel cleaner, Lucas makes a good one as is Techron. They will help with sludge in the injectors but not debris.

  • Richard Scordino May 11, 2010

    Coolant temp seems a bit low if reading is in farenheight, should be at 205-210. Is heat in car normal? If not, change thermostat. everything in the control system depends upon engine being at proper temp (otherwise it thinks its running on cold start-up)
    Taking a fuel sample is not a bad thing to do, but check this out first!



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Check PCV valve and be sure it is not stuck open.  Check for vacuum leak at intake manifold.  

Posted on Jan 01, 2009


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Error code PO171 Mechanic said i need to replace bank One Sensor 2. 89467-42010, 89465-42090, 89467-42020, 89465-42100. Which one do I have to replace?

following answer courtesy of OBD Codes Your OBD-II Trouble Codes Repair Site Home Trouble Codes FAQs Forums Store P0171 OBD-II Trouble Code Technical Description System Too Lean (Bank 1) What does that mean? Basically this means that an oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. The P0171 is one of the more common trouble codes. This code is triggered by the first downstream (front) O2 sensor. The sensor provides a reading of the air:fuel ratio leaving the engine's cylinders, and the vehicles powertrain/engine control module (PCM/ECM) uses that reading and adjusts to keep the engine running at that optimum ratio of 14.7:1. If something is not right and the PCM cannot maintain the 14.7:1 ratio, but rather there is too much air, it triggers this code. You'll want to also read our article on short and long term fuel trims to help understand the operation of the engine. Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time. This diagnostic trouble code (DTC) is a generic OBD-II powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the model. Symptoms You will more than likely not notice any drivability problems, although there may be symptoms such as: a lack of power detonation (spark knock) rough idle hesitation/surge on acceleration. Causes A code P0171 may mean that one or more of the following has happened: The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak downstream of the MAF sensor Possible cracked vacuum or PCV line/connection Faulty or stuck open PCV valve Failed or faulty oxygen sensor (bank 1, sensor 1) Sticking/plugged or failed fuel injector Low fuel pressure (possible plugged/dirty fuel filter!) Exhaust leak between engine and first oxygen sensor Possible Solutions A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include: Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling Inspect all vacuum and PCV hoses, replace/repair as required Inspect all hoses and connections in the air intake system Inspect and/or test the intake manifold gaskets for leakage Check for a dirty fuel filter and proper fuel pressure Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool If you have access, you may want to run a smoke test

Read more at:
OBD II Trouble Codes Home

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PO171 OBD-II Trouble Code Engine Rough Idle When Under Load

Check EGR valve. Also check all injector pulses with NOID light especially when vehicle is stumbling. It may be computer related. Get back to me if you need more help. Good Luck

Dec 28, 2008 | 2000 Jeep Grand Cherokee

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