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Peter Bagley
Peter Bagley, Toyota mastertech
Category: Nissan
Satisfied Customers: 186
Experience:  master tech at Toyota dealer
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Turns over and starts but runs like its running on 4

Customer Question

turns over and starts but runs like its running on 4 cylinder and its a v8 and when you go to give it gas it stalls out
JA: Is the check engine light on? Does the car stall at idle or when driving?
Customer: no iights but did get a code po171
JA: What is the model/year of your Nissan?
Customer: 2004 armada not 4 wheel
JA: Are you fixing your Armada yourself? What have you tried so far?
Customer: Yes. I've already checked the fuel pump for pressure, that seems fine. We put drygas in tank. Still nothing. Cranks but won't start and when it does it's real rough and you can't give it gas.
JA: Anything else you want the mechanic to know before I connect you?
Customer: Someone told me that it was the Mass Flow Sensor but I don't want to buy it if it's not that and it's something smaller. We've never had problems with this car. Out of the blue.
Submitted: 12 days ago.
Category: Nissan
Expert:  Peter Bagley replied 12 days ago.

Hello and welcome to just answer and allowing me to assist you. P0171 NISSAN - Fuel Injection System Too Lean Bank 1. Possible causes;

Intake air leaks- Faulty front heated oxygen sensor- Ignition misfiring- Faulty fuel injectors- Exhaust gas leaks- Incorrect fuel pressure- Lack of fuel- Faulty Mass Air Flow (MAF) sensor- Incorrect Positive Crankcase Ventilation (PCV) hose connection

Possible symptoms;

- Engine Light ON (or Service Engine Soon Warning Light)- Excessive Fuel Consumption

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic). You can easily check for air or vacuum leaks your self but the rest you would need a scanner to watch the oxy senor readings. Hope this gives you some options to go by and if you need further assistance I;ll be happy to do so.