Hi Guys.
Newbie and first post. Great site lots of info. Looked at FSM seems mind boggling without code reader.
My 06 G35 sedan has 186k miles. best car I've owned. It started misfiring intermittent only occasional at high speed. Next day it got worse with hot starts long cranking time and no idle.RPM gauge eratic,VDC off light on and others.and running terrible. It settled down and I made it home @ 30 miles. Nothing has been replaced on Engine ever. except regular maintenance,plugs filters etc. Need advice Thanks.

With that many miles I'd be looking at basic tune-up type things. Spark plugs on that engine are designed to go 90-100K miles, when was the last time yours were changed? Also when was the last time you had your fuel injectors cleaned? The VDC light on issue a lot of times is the result of brakes being worn past specs. Recommended replacement for brake pads is at 2-3mm of friction material remaining. How long ago were they last changed? G's go through brakes, especially rear brakes pretty quickly. If the pads are worn down far enough, the fluid level in the master cylinder will drop to the point that it sets the VDC light.

You've got a few things going on there. If its drivable, then get to an auto parts store (Advanced Auto, Autozone, Orielly's, etc) and have them read the codes for you. Since it happened quickly I'd be checking proper wire connection to the spark plugs. It also sounds like it could be something with Mass Air Flow / Throttle body. Check and /or clean the mass air flow sensor. Before I left the house I would probably do the Re-learn process for the Throttle body.

A. Accelerator Pedal Release Position Learning Procedure.
1. Make sure that the accelerator pedal is fully released.
2. Turn ignition switch “ON” and wait at least 2 seconds.
3. Turn ignition switch “OFF” wait at least 10 seconds.
4. Turn ignition switch “ON” and wait at least 2 seconds.
5. Turn ignition switch “OFF” wait at least 10 seconds

B. Throttle Valve Closed Position Learning
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch is “ON”.
3. Turn ignition switch is “OFF” wait at least 10 seconds.
Make sure that the throttle valve moves during above 10 seconds by confirming the operating sound

C. Idle Air Volume Learning (Throttle Position Learning) Best with a watch/clock...I use my phones stop watch function to do this. (It may take a few times to get the rhythm of this process down).
1. Make sure you've already Performed “Accelerator Pedal Released Position Learning”.
2. Make sure you've already Performed “Throttle Valve Closed Position Learning”.
3. Start engine and warm it up to normal operating temperature.

Turn ignition “OFF” wait at least 10 seconds.
turn ignition switch “ON” wait 3 seconds.
Stomp and Release gas pedal 5 times within 5 seconds.
Wait 7 seconds, fully depress gas pedal for 20 seconds or until (CEL) stops blinking and stays ON.
After CEL is solidly on - Release gas pedal within 3 seconds
Start engine and let it idle for 20 seconds
Rev up the engine two or three times and make sure the idle speed and ignition timing are within the specifications.