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2003 Impala Intermittent Shutter/Buck on quick accel or quick accelerate and quick release of pedal

Greetings! I have a 2003 impala I just bought and it has an intermittent problem. Sometimes when I step on the gas the motor will ‘slam’—kinda like if the motor mounts were bad but they look good and it doesn’t always do this. Also, if I hit the gas pedal hard and then almost as quickly let off the gas pedal I get the same effect–shutter/slam. I suspect the mounts but they look fine. If I keep on the gas all gears shift very smoothly. Gear shift is smooth thru all gears if I floor it or go slowly accelerate so it seems not to be the transmission either. Anyone have any ideas?

Have you checked the level and color of the transmission fluid yet?

I expect your instincts are right, this is a motor or xmission mount problem. I guess what I’d do is have someone watch the engine and xmission, from as many angles as possible, including from below, while gunning the gas. I expect you’ll see that there is extra movement at one of the mounts compared to the others. It might just be a missing or loose bolt or something, but first you need to find where the movement is occuring. If there’s a noise associated with this, then a mechanics stethoscope might be helpful to isoloate where it is occuring.

My 2008 Impala does this also. There was an issue with an electronic sensor regulating fuel and I had to have a unit replaced.$$$ This corrected the problem temporarily but its doing it again. It has gotten worse and the hesitationfollowed by a slam and a burst of speed when I am ducking into heavy traffic on 95 is a bit dangerous at times. I FEEL like it’s related to the transmission but I do not know. If anybody knows why its doing this PLEASE comment. As a side note…the car has also developed several electrical problems; passenger door lock unresponsive, drivers side speakers rarely work, occasionally the windshield wipers stop working, right front tire sensor gives a false read and has been replaced, etc.

I have had these same crazy symptoms in my 2005 Impala, thought it was going to the transmission specialists or the junkyard. I have been using Martin fuel in western PA and it has been miraculously CURED! But other western PA gas has no effect on it. The person at the gas station said that a lot of people need new fuel pumps when they use their competitor’s gas. Thing is, I live in EASTERN PA and when I leave my mother’s house I don’t know what I’m going to do. I don’t think they sell Martin gas in Philly. Any suggestions?

@GEO1, if using gasoline from certain filling stations actually caused fuel pumps to fail, we would be replacing them left and right.
There are millions of people that exclusively fill up at cheap-ass gas stations and never have any problems because of it.

I’m not saying it’s impossible, but it sounds as if Martin is trying to discredit the competition.