Question about 2004 Infiniti QX4

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Cannot accelerate engine past 1/2 throttle without stalling. QX4

(1999 QX4) (No "SERVICE ENGINE" light) The symptom started out as rough to start. It acted like it was starved of fuel. The fuel pump and fuel filter was replaced as well as dist. rotor and cap. Truck ran great for a day. Then it started stalling when accelerating the engine past 1/2 throttle only when it was warm. Now, it does it cold. When it stalls, I can tell it is backfiring because there are exhaust fumes in the intake after a stall. I even re-checked the plug wire routing. All is good. At idle, you can see the tachometer slightly flicker, but it is hard to feel. The fuel filter was replaced again. The fuel was checked for water. The fuel pump lines were inspected. The exhaust smells a little rich. This might just be my imagination, though. I'm drawing a blank and feel a sensor is going out or already has. There is still no engine light. I'm confused and am close to taking it to the dealership. Your suggestions are greatly appreciated.

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  • Jackson Hisey
    Jackson Hisey May 11, 2010

    Try disconnecting the front O2 sensors one at a time. The connectors are located near the oil fill cap on the rocker/valve cover. We only want to unplug the front oxygen sensors. Those are the grey connectors with three pins not four. The four pins connectors are for the rear sensors which would not cause this problem. Unplug one of the sensors and see if the problem goes away, if it does you could have a sensor issue or an injector issue. It is just a place to start. FYI, you check engine light will come on when you unplug the sensors. Let me know how you end up so we can continue the diagnosis.


4 Suggested Answers

  • 37 Answers

SOURCE: 94 j-30 sometimes missing runs rough then 1 hour later runs fine

Check to see if your spark plug wires are not cracked or worn. They would make the engine run rough when cold or damp more often then when the engine drys up when warmed up- just an easy thing to check...

Posted on May 24, 2009

SOURCE: I have an 1999 Infinity

Have your fuel pump pressure tested!

Your car could be running great because its demand for fuel pressure is met at idle. But at part and wide open throttle you fuel pump could be running aground.

A mechanic with a fuel pressure gauge can drive the car around and see if the pressure falls flat during off idle throttling.

Good luck and be careful!

Posted on Mar 19, 2010

  • 2382 Answers

SOURCE: 1998 Infinity Q45

Hi, i would replace the air filter, make sure the air hose from the air filter to the intake is not kinked or blocked and check for vacuum leaks. If these are all fine, I would check the fuel pressure as it is possible the pump is weak and not supplying enough fuel.

Posted on Nov 18, 2010

  • 1874 Answers

SOURCE: will sometimes stall at stops, feels like its

First of all you need to access the Engine Control Module (ECM) using suitable diagnostic equipment connected to the data link connector of the car, in order to pull out all DTC's memored. DTC = Diagnostic Trouble Code. Then you will bu full informed about the root cause of the problem, and you will be able to repair & replace bad pieces and reset the ECM.
Let me know please about found DTC's. I will assist you kindly to fix the problem.

Posted on Sep 05, 2011

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Is the service engine soon light on? I would suspect, based on your description, the TPS sensor may be open or the temperature sensor may have failed.
When you open the throttle the TPS sends the accelerator pedal information to the engine controller so the engine controller can add fuel and allow you to accelerate. If the TPS does not send the correct throttle position to the engine controller, no fuel is added and the engine stalls.
If the coolant sensor has failed, your fuel mixture will not be correct and engine can stall when accelerating.
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