throwing code P507 (idle air control System RPM higher than expected

D

dogburrito

Member
Location
Raleigh, NC
Car
2003 Infiniti FX35 - Rear Drive
Name
John K

My 2003 FX35 (210K miles) is throwing code P507 (idle air control System RPM higher than expected.) The idle speed is high, about 1000 to 1200 RPM. This is a result of my cleaning the TB (first time ever for this car and overdue.) The idle was correct beforehand at 600 to 700 RPM.)

Cleaning the throttle body (lots of black soot took me 30 - 45 min using TB cleaner, Q-tips, paper towels and an old cotton sock.) I reinstalled w. new gasket then did the 3 part pedal dance learning procedure (pedal release position, throttle valve closed position, and idle air volume.) After doing this twice, the idle is high.

Some facts:

I cleaned the MAF using MAF cleaner during this job.

Prior to cleaning the idle speed was perfect (around 600 to 700 RPM)

My objective was to get a smoother idle as there was marked vibration when in drive, idling with AC on.)

This is the first time the TB has been cleaned.

There was no original gasket.

On the bench, the TB valve rests in a partially closed position, about 1mm from completely closed. I can move the valve to fully close it and fully pen it too, without obstruction.


No apparent vacuum leaks unless I cracked a hose unaware.

Any information would be appreciated.

Thanks
 
Ah. Thanks.

I wasn't aware of the ECU reset - Previously, I've done were the Accelerator, Idle Air, and the Throttle valve closed reset procedures.

What does the ECU reset do? Does that simply clear the codes? Or does it also erase the Accelerator, Idle Air, and the Throttle valve settings?
 
I had this issue too while cleaning the MAF. The "pedal dance" took care of it. Timing is critical.


Sent from my iPhone
 
Idle still at 1200 RPM after many time through the learning procedure (pedal dance.)

So I got a Nissan tech on the phone and according to him, the error is that the RPM must be FORCED to the correct RPM before the learning procedure so that the can can LEARN the RPM. . The method is to force the correct RPM by disconnection of 3 or 4 fuel injectors by trial and error until the 650 RPM is achieved.

According to that, I've been doing the learning procedure with an RPM of 1200, and the car just re-learns the 1200 RPM each time

The fuel injectors on the FX35 are beneath the plenum! How is one to use a "trial and error" method disconnecting fuel injectors where the plenum must be removed and replaced with each try?

I'm not sure if this is "ass backwards" or just "kart before the horse".

Anyone do this fuel injector method?

anyone know how to easily disconect fuel injectors?
 
I have not heard of this injector method. There is no way to disconnect the injector other then at the injector. I would disconnect the battery overnight and try the pedal dance again.
 
First I'll try disconnecting the battery....

The injector method is discussed on several Nissan blogs to force the desired idle RPM before the learning procedure. One mechanic said that he disconnects 2 or 3 coil connectors but I'd be concerned about sending unburned fuel & air into the catalytic converter. If I must force the idle RPM lower then I suppose that constricting the air at some point before the MAF is an option.
 
Resolved.

What worked: Forcing the idle to the desired RPM before the learning procedures. There is one fuel injector within easy reach using long long-nosed pliers (the #1 cylinder - nearest the coolant reservoir.) Disconnecting it brought the idle down to 750 RPM (from 1200.) Not the 650 per spec, but good enough.

Then I did the 3 part pedal dance learning procedure (pedal release position, throttle valve closed position, and idle air volume.) The idle then stuck at 750 after reconnecting the injector. I can live with that and so can the ECU since it wont throw a "high idle" code within 200 RPM of the specification.

Note: the idle needed to be at the desired RPM beforehand, since the learning procedure learns that RPM.

Observation: while the idle speed was out of whack (1200 RPM) during the past 2 days, my in-town gas mileage really suffered and read at about 6 MPG (where I'd expect about 15 MPG.) After fixing the idle I drove a familiar 23 mile highway circuit with the cruise set to 60 mph and got about 29 MPG (about a 5% improvement from previous trials.)

Also, the rough idle (while in drive w. AC on) is improved.

Prior to all this, I disconnected the battery for 12 hours (before doing the 3 learning procedures.) This did not work.


 
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