I was on the freeway, driving at around 75mph and cutting into lanes. I accelerated to cut a slow driver in the fast lane and felt the engine bog/stumble. At first, I thought my clutch gave out. I immediately changed lanes and drove in the shoulder lane at around 45mph so I can make it to the next exit. For about a mile, I would downshift from 6th to 5th to 4th then back up to 6th. Clutch felt fine, the RPMs would increase a few thousand and then the car would bog/stumble again. It came to the point where I could not accelerate past 45mph and I believe that the engine would start to bog/stumble in the low RPMs.

I drove up to a red stoplight. I sat there in idle and kept pressing on the gas. The car would rev to a certain point and then bog/stumble, making the car jerk intermittently. When it hit green, I pressed on the gas in first gear and the car started to bog/stumble but it was able to accelerate enough to cruise into the plaza parking lot. I parked and let it idle. It would idle fine and then bog/stumble to where it would sound like it dropped to a lower RPM idle, then back up, and repeat.

I shut the car off for a few minutes. Started the car and everything was fine. I was like WTF? So I turned it off again. Started it back up. Seemed fine. I revved and there was no bog/stumble. I ended up being able to drive the rest of the way home (25 miles) with no issue. I was too worried to hit the gas and drive past 70mph.

What do you guys think this might be? This is the first time it has ever happened. I own a '08 G37S MT. Spark plugs were replaced already around 100k. My baby now has 176k on it.

Note: my fuel was low and I gassed up at Valero up til 3/4 tank. While it was pumping, the pump kept stopping. I'm thinking I may have filled up on bad gas. Planning to buy fuel system cleaner at the nearest auto store at least for now.

 

Something triggered limp mode. And, there is a TSB for fuel filling issues.

 

I never knew what limp mode was until it happened today. Thanks for pointing out the TSB. I'll be letting the dealership know about that one.