digiera

08 G37S Coupe goes into limp mode 4 times over past month. I'm new owner so I don't have any history except the previous owner said he didn't drive car much. So far it only does it within 50 miles of adding gas and on highway. Always use Chevron highest octane. Sure would like to troubleshoot this without going to dealer. No error codes or check engine light.
Any thoughts are appreciated.

SonicVQ

Describe exactly what happens when it goes into "limp mode"
Is there a check engine light on?

telcoman

Limp mode is designed to prevent an engine or transmission malfunction from causing further damage to the vehicle.
Since you are not receiving any error codes or CEL perhaps it is something deeper in the vehicle computers?

A dealer Consult lll should be able to find the root cause.
Call your local dealer and ask questions from the service manager.
Perhaps they will want you to bring the car in the next time it happens?

Just my $.02

Good luck

Telcoman

canucklehead

iTrader: (9)

the only time i went into limp mode was for the blown rear timing cover gasket. but i had error codes when that happened so if the OP has no error codes and is still in limp mode something is haywire. get in to see an experienced Nissan tech with Consult equipment for a diagnosis.

SonicVQ

Well... I guess my speed reading failed me.

digiera

Just wish I didn't have to go see a dealer......

SonicVQ

Let me ask again: When it goes into limp mode, what are the symptoms?

digiera

It seems to occur within 50 miles of refueling and at highway speeds. Also the engine is at operating temperature. When it occurs, the engine will not run over approx 2500 rpm and if it does reach 2500 it shakes violently until back down below 2500. If you pull over and shutdown, it will restart and run fine. No error code that I can read with my cheap device. Also no CEL. The violent shaking is really violent and it feels like theres a big chain attached to the axle stopping the car from moving forward.

dmg6768

iTrader: (3)

Go to the auto parts store, plug in code reader check for codes. Sometimes codes will be stored that do not illuminate your Check engine light.

SonicVQ

OP: Good info!

If the engine won't rev above:
(1) 2,000 RPM there is an issue with the Electric throttle control actuator.
(2) 2,400 RPM there is an issue with one of the MAFs / or engine oil pressure
(3) 3,500 RPM there is an issue with the VVEL actuator motor / relay

The lowest cost next step is to get an ELM327 and a app (Torque or OBD Fusion) and look at your "mode $06" data. (assuming your scanner does not read mode $06)

Mode $06 is a series of tests that are run on your car as you drive it. It also has counters that can tell you if the car has misfired. I suspect you will find some failed items in the mode $06 data, and that is your first clue to finding out what the root issue is.

If the above is not for you, then take it to a shop and have them scan and print the mode $06 data.

digiera

Sonic VQ,
Thanks for the info. I have an ELM327 but only used it with car running but stopped - no error codes. I'll try it while driving. My app is DashCommand and I don't see any $06 yet.

digiera

Couldn't find an $06 option. Connected ELM327 and before driving I had one Pending Code (P0174 System Too Lean Bank 2). Then drove 1/2 hour and nothing else. I guess I need to find an app with $o6.

SonicVQ

The Android app "Torque" has mode $06 data under the "Test Results" sections.
For iPhone/iPad the "OBD Fusion" app has it under Diagnostics -> Mode $06.

The pending code "P0174 System Too Lean Bank 2)" tells us that this issue has happen ONCE. When it happens a second time, a check engine light will shown.

I suspect your fuel trims will be VERY positive (>10) on bank 2. I think Dash Command can see live data (aka mode $01) if you make a new gauge.

Check the driver's side of the engine (bank 2) for any loose/cracked hoses. Make sure to check the hose that connects the valve cover to the intake. (between the MAF and TB)

digiera

Thanks Sonic, I'll be checking back in later to report my findings. Already cleaned both MAFs.

mcheema

I have the same problem on my 2008 G37S, went to the dealership and they couldn't replicate the problem, instead they decided it was time to replace my battery and upgrade the ECU... When I read the engine code it says its in relation to the MAF and I'll be replacing them soon. This problem is extremely dangerous especially on the highway and I'm surprised nobody has found a solution for it, its such a random occurrence when it happens.

Its a very scary situation when you're going 100-130km/hr on the highway and your car just decides to stop and jerk itself back and forward.