Why does my car lack acceleration then stutter sometimes?

I have a 2002 Subaru Impreza 2.5TS. I have been dealing with this for a while. My car needs a replacement intake manifold gasket and needs the knock sensor wire harness replaced. So currently, there is a minor leak in the intake and to my knowledge, the knock sensor is currently not working.

Barring those issues that I am working on solving, my car has trouble accelerating, especially when going uphill. Sometimes, I will put my foot down on the pedal and nothing will happen, in fact I have seen the RPM dip occasionally when I am trying to accelerate. Following this, so to mean, after it has trouble accelerating, it then proceeds to sputter and stutter a bit, each stutter separated by a few seconds. It will give anywhere from 3 or 4 stutters to 10 or so. During these stutters, the car loses speed to the point that I as a driver, jerk forward and can see the RPM drop down. When the RPM drops and stabilizes, the car runs pretty normal again until the next stutter.

I notice that when I only put my foot down very gradually and go up no hills, the car will not show any signs of this stutter and drive normally, besides the need to accelerate rather slowly.

Anyone have any idea what might be going on? Of course, besides the intake and knock sensor which will be sorted out soon.

Has anybody tested the throttle position sensor?



I’d think the intake manifold leak and knock sensor could cause the acceleration issues. Need to fix that first.


No they have not, what would I look for if it were bad?

Definitely, thank you!

My mind thought of clogged or failing catalytic converter, or some other kind of exhaust restriction.

On a 2002 model anything, it’s certainly possible.