EX Shuts down at higway speeds

[janemackey]

Hi, I'm after any information for a recurring problem with no solution as of yet. A few months ago, while driving on the interstate going approx 75 mph, my 2008 EX just shut down, losing acceleration quickly. However, the car's power did not turn off, the steering was not lost and I was able to move over onto the shoulder away from semi-trucks etc. Turning off the car, I attempted to restart, and although the car immediately turned on, I still had no power. Pressing on the gas pedal did nothing. A few times more, it caught and I was able to get home.

The Infiniti service department found nothing and everything was fine for several months. However, the same thing happened again yesterday, traveling again at highway speeds. Power just shut down, without loss of steering or radio etc.

Any ideas? Scheduled to take it in, but they haven't heard of the problem.

THanks!
J Mackey

[NJGuy]

So you're saying the engine never actually dies and continues running, right? What did the tachometer (RPMs) show when you were hitting the gas pedal in these situations? Would the engine rev higher when you hit the gas, or would the RPMs stay low?

It could be a throttle or transmission issue, but right now I'm leaning towards the throttle. I think that the EX's throttle is drive-by-wire, and I'm not familiar with the details of how it works. Maybe someone who knows the inner workings of the drive-by-wire system can comment and either confirm that it is related to your problem or rule it out entirely.

The fact that the car's issue is sporadic and difficult to duplicate makes this a tricky problem to solve. Good luck, and stay on the service department's back as this is a safety issue.

[janemackey]

Thanks for your thoughts......the rpm's show nothing......its like there is no contact between the gas pedal and the engine, and the way the speed actually decreases rapidly, without any coasting as such, is so weird......like I'm driving along, radio on, and the speed just suddenly drops and as I instinctively push the gas there is nothing. The car slows so quickly but the steering and electrical on the dash, is all working. There is barely enough time to change lanes and get over to the shoulder. Turning the car off then back on, it immediately starts back up but the gas pedal still feels unconnected and does nothing to up the rpm's. After a few times of turning it off and on, it catches and i was able to stay near the shoulder but drive home. Of course it works fine now, two days after that event. However I'm NOT taking it on the highway until something is figured out.

[AWGD8]

How is the key battery ? Is it new battery? Maybe your immobilizer kicks in?

Check for lose vacuum hoses near the intake and throttle bodies...

Maybe try Shell V power 93 octane first, not sure if there is a clog in fuel lines or Fuel pump intermittent failure...?

Can you do these procedures?

NOTE: Please read all instructions and be familiar with them before any attempts. Timing is extremely critical. If it is NOT DONE within the specified time, the ECU will not reset and the Check Engine Light (CEL) will continue to remain ON. There is NO margin of error. A stop watch or an analog clock with a second’s hand is mandatory.

<u>Basic ECU Reset</u>

Operations Procedures:

1. Confirm that accelerator pedal is fully released, turn ignition switch “ON” (NOT start) and wait 3 seconds.
2. Repeat the following steps (2a and 2b) procedures quickly five times within 5 seconds.
2a. Fully depress the accelerator pedal (HARD).
2b. Fully release the accelerator pedal.
3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 10 seconds until the CEL starts blinking.
4. Fully release the accelerator pedal (while the CEL is still blinking)
5. Wait about 10 seconds.
6. Fully depress the accelerator pedal and keep it for more than 10 seconds.
7. Fully release the accelerator pedal (The CEL light will continue to blink).
8. Turn ignition switch to “OFF” position and now you can start the car. The CEL light should be gone. If the CEL light continues to remain ON, repeat the above steps. Remember, timing is EXTREMELY critical to resetting the ECU. You may even need someone's help to do this correctly.

Much easier to do if you watch this while doing the procedure.

http://m.youtube.com/watch?v=95WszTnphP ... 5WszTnphPI

I just watch this on my IPad and I just follow the guys count down...


Note: The following reset procedures are directly from the 2004 G35 Sedan Service Manual.

<u>Accelerator Pedal Released Position Learning</u>

Description:
Accelerator Pedal Released Position Learning is an operation to learn the fully released position of the accelerator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time harness connector of accelerator pedal position sensor or ECM is disconnected.

Operation Procedure:
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON and wait at least 2 seconds.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON and wait at least 2 seconds.
5. Turn ignition switch OFF and wait at least 10 seconds.


<u>Throttle Valve Closed Position Learning</u>

Description:
Throttle Valve Closed Position Learning is an operation to learn the fully closed position of the throttle valve by monitoring the throttle position sensor output signal. It must be performed each time harness connector of electric throttle control actuator or ECM is disconnected.

Operation Procedure:
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
Make sure that throttle valve moves during above 10 seconds by confirming the operating sound.


Also, you can clean the throttle bodies using this

http://www.autozone.com/autozone/access ... fier=55922

Make sure you do not flip open the throttle body plates. Just clean around the plates and soak it while it dissolve those gunk. Use a cotton ear bud to clean around it.
I heard that if you open the plates, it messes up the electronic throttle positioning sensor and you would end up having an engine check light codes. Please be very careful , so you would not end up buying a pair of throttle bodies....

[meanie]

Thanks for your thoughts......the rpm's show nothing......its like there is no contact between the gas pedal and the engine, and the way the speed actually decreases rapidly, without any coasting as such, is so weird......like I'm driving along, radio on, and the speed just suddenly drops and as I instinctively push the gas there is nothing. The car slows so quickly but the steering and electrical on the dash, is all working. There is barely enough time to change lanes and get over to the shoulder. Turning the car off then back on, it immediately starts back up but the gas pedal still feels unconnected and does nothing to up the rpm's. After a few times of turning it off and on, it catches and i was able to stay near the shoulder but drive home. Of course it works fine now, two days after that event. However I'm NOT taking it on the highway until something is figured out.

I have never had this happen to me with any car, but it sounds rather like the car is going into "limp" mode. As I understand it this is a protective mode the car goes into when something overheats (i.e. engine oil, cooling system, etc) that keeps the engine from further damage by severely dropping the rpms. Folks who tracks their cars sometimes report this occurring due to sustained high revving, and I think once the car cools down a bit regular power is restored. IF this is the case it clearly should not be happening at typical highway speeds and something else (bad sensor, or perhaps some overheating?) is causing it. Anyone more familiar with limp mode able to comment on whether this might be the case?