2001 Pathfinder stalls after idling for 25 seconds

[theppler]

My 2001 Pathfinder has gradually "acquired" this little problem... While driving, it runs great. I'll try to describe what happens when I pull up to a stop light:-engine idles down to 750 rpm exactly as expected.-after 25 seconds exactly (I've timed it), the idle speed drops down to 500 rpm or lower.-sometimes, the engine stalls out at this point-if the engine does not stall, it takes a couple seconds and then comes back up to 750 rpm

One interesting thing that I kind of stumbled upon by accident relates to this thread:zer...valve The thing I was asking about is the Swirl Control Valve (SCV) tank. It's basically a one-way valve with a vacuum accumulator tank on it. If I disconnect the hose from that tank and run the engine, this idle stall problem I described does not happen. Although it threw me a P1130 (Swirl Control Valve Solenoid problem) code as expected.

I've tried the Idle Air Volume Learning procedure as described in the FSM but the problem remains the exact same.

If anyone has any thoughts, I'd appreciate the input.

[pm_page6776]

Without being able to look at your vehicle, I would say you may have a bad mass airflow sensor causing a rich condition. When you disconnect a vacuum hose, you lean out the air-fuel mixture and improve the condition. Does it improve when you disconnect any vacuum hose the same size or only the swirl control valve? If you have access to a computer scanner, you should check your air/fuel alpha (fuel trim) to see if it is running rich or lean.

[theppler]

Thanks for the input . I'll try disconnecting another vacuum hose to see. I have noticed that after running it in my garage for a minute, the exhaust does smell pretty rich if you know what I mean.

I only have a real-time OBD2 scanner that connects to my laptop (not a Nissan Consult scanner). I don't think this vehicle reports the air/fuel alpha through the OBD2 though. I'll check it out again.

If the rich condition is the problem, would you suggest that I carefully try to clean the MAF sensor before replacing it?

[theppler]

I wasn't really sure what other vacuum hose to disconnect so I did some diagnostics on the MAF sensor itself. Here is what I measured on the output of the sensor (in brackets are what the field service manual says it should be):-Ignition switch on, engine stopped: 1.22V (should be approx 1.0V)-Idle, normal operating temperature: 1.56V (should be 1.2-1.8V)-2500 RPM, 2.05 (should be 1.6 to 2.2V)

So it looks like it is reading a little high but still within spec.

I also did some diagnostics using my OBDII scanner and found the following:

At 0 RPM: -MAFS reads 1.92g/s -Short Term Fuel Trim (Bank 1) reads 0% -Long Term Fuel Trim (Bank 1) reads -3.9% -Short Term Fuel Trim (Bank 2) reads 0% -Long Term Fuel Trim (Bank 2) reads -3.1%At 762 RPM (idle): -MAFS reads 5.11g/s -Short Term Fuel Trim (Bank 1) reads -19% -Long Term Fuel Trim (Bank 1) reads -14.1% -Short Term Fuel Trim (Bank 2) reads -18% -Long Term Fuel Trim (Bank 2) reads -13%At 2575 RPM: -MAFS reads 12.62g/s -Short Term Fuel Trim (Bank 1) reads -0.8% -Long Term Fuel Trim (Bank 1) reads -14.1% -Short Term Fuel Trim (Bank 2) reads -2.3% -Long Term Fuel Trim (Bank 2) reads -13.3%

I don't fully understand what these fuel trim percentage numbers mean. Is it strange that all numbers are negative at all engine speeds?

[Nuisance Nissan]

Were you ever able to fix this issue with the idle stumbling after 25 seconds? I am having the same problem. The dealership told me it was the idle air control valve motor, but I tested it with an ohm meter as recommended in Chilton manual and it appears to be fine.

Whatever the cause of the problem is it appears to be getting worse because the motor has started making a noise I've never heard before in the 92K miles that I've had it. I sounds similar to a Jeep engine now (it's that weird wheezing sort of noise that's so noticable especially in Jeep Cherokees when you first start them).