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Matt, Engineer
Category: Subaru
Satisfied Customers: 21706
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have a '15 2.5 Forester with 18k. When I depress the accelera

Customer Question

I have a '15 2.5 Forester with 18k. When I depress the accelerator I don't get the smooth application of power but a surge. It is controllable but disconcerting. The dealer says "normal" but I doubt that the designers and builders intended this. Is it normal? Can it be adjusted out?
Also, when I put the variable drive transmission in gear, either forward or reverse, it takes 2 to 2.5 seconds before it engages. That is a long lag time, much longer than the automatic transmission I am used to. Was that lag designed into the trans or is it an inescapable characteristic of the variable trans?
Submitted: 2 years ago.
Category: Subaru
Expert:  Matt replied 2 years ago.
Hellothe CVT can give some odd feelings when compared to a regular transmisson however the lag in gear selection isn't right and the sudden surge also isn't normal so I'd suspect the transmisson either needs a oil change or a software update - due to its age and milage I'd say the software is the 1st thing to try
Expert:  Matt replied 2 years ago.
do you still need help?
Customer: replied 2 years ago.
I was attracted to the "just answer" site as a result of being shown, and I assumed, being connected to a Subaru master mechanic with 20 years of Subaru experience as the person I would be dealing with, not an engineer with several years of F1 experience. I don't believe that your expertise, though considerable on those vehicles, is transferable to my situation.
The surge I referred to is engine caused, not trans. In the old days I would have attributed it to a carburetor flaw, but this has no carburetor.
Expert:  Matt replied 2 years ago.
OK if you would prefer another expert I'll opt out
however if you feel the transmisson is not to blame then the next option would be a possible air / vacuum leak
The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.
Expert:  Matt replied 2 years ago.
do you still need help?