Pulsing Acceleration
 

I have a 2008 Forester XT auto, cobb access port, downpipe, and a protune. While accelerating, giving it a good bit of fuel, the car will pulse in rpm up and down. Each pulse up and down is about a second long up, down, up down, until you either bury the gas pedal or remove your foot from the gas. It only happens while the car is tuned -- both the cobb over the counter tune and the pro tune have the same results. has anyone had the same problem before?

not one person? no ideas? fuel pump?

How cold is it where you live? I had this a problem last winter. Fuel tank condensation turned into ice and gumming up my fuel filter.

California. we all ***** about 40, likes its the end of the world. no ice or snow.
i hear a noise when i start that sounds like the fuel pump is bubbling. granted it goes every time and has nothing to do with the tune, but maybe its fuel related?

update: removed the tune. got 105k and 120k service done, everything that was touched was replaced. not that suggested dealer crap. turned the tune back on to stage 1, otc. works great now. no pulsing. i have no idea what it could have been. putting the dp back on this weekend. we will see.

weird how thing get solved with out really knowing what did what. at least you're now good to go.

the issue is back again. even with full exhaust and tune. ugh.

800 people have looked and not one other person has this issue? amazing.

i have a 2008 AUTOMATIC XT. full exhaust, and when you pull light in high gears, is pulses up and down like its starving. my guess is fuel related. could this be the cause? perhaps the injectors cant handle the change in output? anyone?