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Hello. I have an automatic and I thought it had something to do with the transmission. I thought it was the a/c too. Come to find out it was one of the ignition coils. When I took off from a stop it went away. I could also feel it while maintaining a steady speed at ~2000 rpm.

 

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Hey chief, do you have a cvt transmission? I forget.
They love to do weird sh*t when fluid is old and capacity is off.

For a little comparison, I was feeling reduced/laggy acceleration after doing a valve job with tappet gauges that were a little too far towards the loose/closed end of the spectrum. Off the bat I thought valves. But I also noticed vibration when slowing at freeway speeds..
After some testing, I realized it was in large part my brake rotors (still gonna readjust valves though!) which had warped. Caused pad rubbing which caused lag.

I'm almost positive you've got an automatic tranny, so start there, yeah?
All ac should do is increase load on the powerplant. could magnify some pre-existing buggery!

 

I had this same exact problem in my 09. It did this for probably 30,000 miles before eventually stalling out on me. Replaced ignition coils and spark plugs and works good as new. Sorry to hear ignition coils didn’t fix your problem, but that’s exactly what I experienced when mine needed replacing.

 

OP mentioned replacing coils, but I wonder if the spark plugs were replaced too or if they were, did something go wrong there?

I'm having trouble wrapping my head around the "lunge" forward issue... like, if the brakes were by wire instead, it could imply a loss of power allowing the vehicle to move again. But the brakes are hydraulic, so that's unlikely.

Is it a "surge" in the engine? One guess could be a long standing loss of power from a "not quite working" cylinder(s) that suddenly works (correctly) again. But that's unlikely I guess.

Or maybe it's a lot simpler that all that. With the AC on, the compressor occasionally comes on and that requires the engine to increase RPM a bit to avoid stalling (as it has to spin the compressor along with everything else). And that it's not really "jumping" significantly, but only just noticeably due to the coincidence of it occurring at that time, not actually stopped, but slowing down to stop.

 

For my situation personally it definitely seemed like a lunge from a surge in power. Cylinder 3 wasn’t firing and it resulted in a very very rough idle. Car felt like it was going to die before lunging forward. When in motion it wasn’t something you really noticed, never had any problems until my car stalled out on the freeway a few times. After replacing spark plugs/ignition coils it runs better than I can ever remember at 180,000 miles.

 

That sounds like when my spark plug ports went bad. The thread started to fail, requiring me install inserts.