@Zeerok: I'm glad to hear that.

I believe the factory plugs are Iridium-tipped and when they stop working, it's very unpredictable. They're great right up until the point they don't work well at all. That's why I'm replacing my factory spark plugs next month on my '10 FEH Limited even though the ICE is running perfectly.

Also: I'm not sure how long the original plug wires last, but they're certainly getting old at 12+ years, so I'm thinking of replacing them too.

At the age of these cars, you have to think of *preventive* maintenance. Make sure you've also changed the transaxle fluid. Change the air filter. Etc., etc.

 

I am having the same exact issue in my 07 FEH. Did the spark plug replacement end up fixing the issue for good?

 

The spark plug replacement definitely seems to have helped. I thought it was solved totally but then it's happened a couple more times recently since the weather has been colder. For me it only happens when it's cold (low 40s or under) and when accelerating on an uphill grade at high speed (60 MPH or above). Letting up a bit on the accelerator makes the bucking stop.

I think that the disconcerting bucking is just the way that this vehicle behaves when the engine misfires or hesitates for whatever reason. In a regular ICE car, a momentary loss of torque from the engine isn't felt very much at the wheels when the transmission is in a higher gear. But in this fancy computer-controlled hybrid transmission, the unexpected loss of torque confuses the computer and whatever it tries to do to compensate is immediately felt at the wheels. Anyway, that's my latest theory.

 

Have you tested fuel pressure? Sounds like it could be a fuel pump/fuel starvation issue as well.