I recently bought a used 2008 G37s with the 5at/manual mode/paddle shifters.. I've been playing around with it and having a lot of fun, but I've had a recurring problem when downshifting into 2nd on hairpin turns, or even when making a quick left turn in traffic (In DS mode). It doesn't do it all of the time so I'm not sure if it is a problem, or just driver error..
When I'm braking into a corner and try to drop from 3-2 there is a terrible lag lasting 3 seconds or so. The engine doesn't rev or anything. The car just rolls for several seconds until it finally grabs 2nd and goes. Like I mentioned, this happened twice while simply making a left at a green light. I downshifted into 2nd while making the turn only to have the car lag so badly I had to switch it back into full auto just to get out of the way of oncoming traffic!
I read in another thread that tapping the brake before downshifting could help, but in the case of hairpin cornering, I'm already on the brake when I downshift. Another technique someone mentioned was lifting off the gas before making the shift (somewhat like manual shifting, but without a clutch).. I haven't had the opportunity to really try these techniques, but I'm wondering if this is a mechanical/electrical issue that I should have checked out, or if I'm just not shifting correctly.
One more thing.. I live at 7200 ft elevation. I have had shifting issues with almost every automatic I've owned since living here due to the vehicles having a difficult time breathing in the thinner air. Usually, a cold air intake modification does the trick. I'm currently running the stock air intake on this vehicle and think this might be part of the problem. Generally, a vehicle loses 20-25% of it's HP up here which could confuse the transmission.. But, in full auto mode, the car shifts brilliantly. No problems.. Any info or suggestions would be helpful

 

Have you tried disconnecting the battery to reset the computer?

 

any slip lights on the dash? Could traction control be perceived as the lag?

 

Thanks for responding. @Zenziglar, there are no codes or lights whatsoever. I've heard about this lag from other drivers on other threads, but no one seems to have a solid answer to the problem. I forgot to mention, the same thing happened while trying to pass someone dropping from 4-3. I moved into the passing lane, downshifted to pass, (around 50 mph) put the pedal to the floor, no revs, and it just rolled as if it stalled for 3 secs then kicked in, but by that time, I had to pull back behind the other driver.
@Hermitmaster, I haven't reset the computer, but I'll give it a try..

 

I think I might chalk this one up to driver error. I took it out today and tried a couple of diff things like letting off the gas before the shift. I think the problem is that I'm downshifting too late. I hit the paddle at almost the same time as I throttle, not allowing enough time for the car to respond. If I downshift half a sec earlier, there is no lag at all. I also think once I add the cold air intakes the shifting will respond a little quicker if the car can get more air.. Thanks again for your responses