Intermittent Engine Low RPM and Stall Upon Start

[PauleyDucati]

Over the last few months my 2012 4.6 sedan will stall out once in a while on a cold start.

IF this happens after a cold start, occasionally it will stall in subsequent warm starts after parking at destination and restarting to leave. No warning lights or codes ever come up when this happens. It never stalls after I start to drive, the car drives perfectly forward and back once I start to move but just sitting there at idle after the initial failed start, the car will run at very low RPM and idle unevenly, eventually stalling. Occasionally random weird warning lights I've never seen in my life will pop up but if I shut down and restart, the lights go away and stay off. This also happens randomly and is not associated with the stalling as far as I can tell as they haven't happened together yet.

The only recent changes I have made to the car were a new air filter and new spark plugs (Iridium, as I could not find out any information on the OE plugs other than the fact that they were NGK). I feel like this started happening a few months after I changed the plugs but it was so rare and subtle I didn't really pay attention. Now it happens more frequently. Does anyone know what type of plugs the 2012 4.6 liter is equipped with from the factory? I wonder if I put the wrong material plugs in the car. My old 1999 Infiniti Q45T required copper plugs only. I tried Platinum to give her a little treat and the she ran like absolute GARBAGE until I put copper plugs in her again.

Anyone else run into an issue like this? I haven't been able to find a single piece of information about this problem. Figured I would chime in here before I go out, swap plugs and start tearing things apart.

 

[Gunkk]

Fuel, Spark, Air, Compression. Need all 4 to run. Weak idle seems more like an air/fuel problem than a spark but you never know.

Suggestions: Use top-tier fuel. TOP TIER™ Gasoline Brands Buy a couple tanks of premium and toss a big bottle or two of techron (polyetheramine) in the tank to help clean the injectors. Also make sure your air filter and throttle body are clean.

Troubleshooting idle and stall from the 2012 4.6 manual:



You want iridium plugs. Denso Bosch and NGK are generally fine; NGK is the OEM IIRC. FWIW not sure what a "type T40246P" is... google is no help. I checked Rockauto and Advance Auto Parts and they show all 1.1mm gap (listed as 0.044") Iridium plugs are in the $15ish range ea. You can spend less on a lower end plug, but I wouldn't.

This thread may be of some help: 2014 R-Spec 5.0 spark plug change



Torque to 20 ft-lbs.

 

[PauleyDucati]

Thanks a lot for the specs. I will have to dig into it further then.

 

[Ozy44]

Over the last few months my 2012 4.6 sedan will stall out once in a while on a cold start.

IF this happens after a cold start, occasionally it will stall in subsequent warm starts after parking at destination and restarting to leave. No warning lights or codes ever come up when this happens. It never stalls after I start to drive, the car drives perfectly forward and back once I start to move but just sitting there at idle after the initial failed start, the car will run at very low RPM and idle unevenly, eventually stalling. Occasionally random weird warning lights I've never seen in my life will pop up but if I shut down and restart, the lights go away and stay off. This also happens randomly and is not associated with the stalling as far as I can tell as they haven't happened together yet.

The only recent changes I have made to the car were a new air filter and new spark plugs (Iridium, as I could not find out any information on the OE plugs other than the fact that they were NGK). I feel like this started happening a few months after I changed the plugs but it was so rare and subtle I didn't really pay attention. Now it happens more frequently. Does anyone know what type of plugs the 2012 4.6 liter is equipped with from the factory? I wonder if I put the wrong material plugs in the car. My old 1999 Infiniti Q45T required copper plugs only. I tried Platinum to give her a little treat and the she ran like absolute GARBAGE until I put copper plugs in her again.

Anyone else run into an issue like this? I haven't been able to find a single piece of information about this problem. Figured I would chime in here before I go out, swap plugs and start tearing things apart.

Any codes? Sounds like a vacuum leak issue. Maybe you knocked something off when you did the plugs? Also, try cleaning the MAF sensor and throttle body if you have not already done so.

 

[GennyRSpec]

Over the last few months my 2012 4.6 sedan will stall out once in a while on a cold start.

IF this happens after a cold start, occasionally it will stall in subsequent warm starts after parking at destination and restarting to leave. No warning lights or codes ever come up when this happens. It never stalls after I start to drive, the car drives perfectly forward and back once I start to move but just sitting there at idle after the initial failed start, the car will run at very low RPM and idle unevenly, eventually stalling. Occasionally random weird warning lights I've never seen in my life will pop up but if I shut down and restart, the lights go away and stay off. This also happens randomly and is not associated with the stalling as far as I can tell as they haven't happened together yet.

The only recent changes I have made to the car were a new air filter and new spark plugs (Iridium, as I could not find out any information on the OE plugs other than the fact that they were NGK). I feel like this started happening a few months after I changed the plugs but it was so rare and subtle I didn't really pay attention. Now it happens more frequently. Does anyone know what type of plugs the 2012 4.6 liter is equipped with from the factory? I wonder if I put the wrong material plugs in the car. My old 1999 Infiniti Q45T required copper plugs only. I tried Platinum to give her a little treat and the she ran like absolute GARBAGE until I put copper plugs in her again.

Anyone else run into an issue like this? I haven't been able to find a single piece of information about this problem. Figured I would chime in here before I go out, swap plugs and start tearing things apart.

Hey, I figured out the fix for any Genesis stalling or failing to hold idle on any startup. Fixed all rough idle.

GDI valve cleaner by Lucas or CRC. Cleans the valvetrain a bit along with the throttle plate, then follow up with Cataclean or Lacquer Thinner to clean the catalytic converters. This process helps air intake, valve seals, and cleans 02 sensors

 

[PauleyDucati]

Any codes? Sounds like a vacuum leak issue. Maybe you knocked something off when you did the plugs? Also, try cleaning the MAF sensor and throttle body if you have not already done so.

The car has never thrown any CEL codes since I've owned it, just TPMS once in a blue moon (I assume the TPMS sensors are reaching the end of their lives). I will look into cleaning the MAF sensor and the valve cleaner Genny suggested... Although she has not done this in a while now so thats odd. She was in the body shop for the last month thanks to a pile of trash that backed into her left rear quarter while parked at a restaraunt. Of course they didnt leave any notes or anything. Ill drive for a while and see if it comes back. Thanks for the suggestions!

 

[toxicavenger70]

Hey, I figured out the fix for any Genesis stalling or failing to hold idle on any startup. Fixed all rough idle.

GDI valve cleaner by Lucas or CRC. Cleans the valvetrain a bit along with the throttle plate, then follow up with Cataclean or Lacquer Thinner to clean the catalytic converters. This process helps air intake, valve seals, and cleans 02 sensors

You have any data to back up these claims? Please don't tell me Scotty recommended this so it is legit.