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Subaru Forester Speed Control/RPM Surge Problems

bkwaasbkwaas Posts: 2
edited July 2014 in Subaru
I am contemplating buying a 2007 ForesterXT sports auto. I test drove the vehicle and like it. But I have read some disturbing things about a surging problem, at least in 2006 Foresters. According to the complaints I've seen, this sometimes seems to occur when the Forester (trimline unspecified) is traveling downhill. Another driver indicated that occurred when he/she took his/her foot off the accelerator before slowing down.

It appears that Subaru has attributed the problem to a drive by wire system. One person who posted something about this a year or so ago indicated that it affected "thousands" of Foresters.

Can anyone tell me more about this problem and what, if anything, Subaru has done/does to address it? I know several people who own Foresters and love them. But this kind of report gives me reservations about buying the vehicle. Thanks in advance.


  • subearusubearu Posts: 3,613
    I have an '04 Forester XT w/ MT and have never had any surging. It was the first year for the drive by wire system back in '04. I don't recall seeing complaints on the Edmunds forums, but perhaps I just haven't been in the right forum.

  • bkwaasbkwaas Posts: 2
    Thanks, Brian. I believe that the problem began in 2006, but I am not certain. There are several complaints about it on this site under "Subaru Forester Engine Issues". In particular, gman67's post titled "high idle".

    There are also references to the problem on Google's "" news group, under the posting "surging Forester".

  • paisanpaisan Posts: 21,181
    Is it surging on downhill off throttle with an AT? If so it could be the transmission doing a downhill decent engine braking thing. I know on my Armada and my Trooper both of which had a feature that will esentially add engine braking, surging the engine, if you completely remove your foot from the throttle.

  • xwesxxwesx Fairbanks, AlaskaPosts: 13,153
    My 07 Outback does this as you describe, Mike, (with MT, even!) when holding speed or especially when taking foot off the throttle, and going downhill. It feels somewhat akin to a firm braking, then completely letting off the brakes, then firmly braking again. It is not a smooth process.

    I do not think it is dangerous - certainly not an RPM surge - but it is acutely noticeable. I think I am getting used to it though because it does not seem as pronounced now as it did when "new."
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • I have a 07 forester 5 speed. Going downhill w/ CC on it speeds up, going uphill it slows down, +/- 8mph. When not using the CC it is very sensitive to throttle imput from no throttle to very little throttle; it induces a jerky motion. This happens in any gear, at any speed, the more bumpy the road (thus more foot input to the throttle) the worse. At cruising speeds around sweeping corners in tight traffic this can be unnerving! The only answer is to put in the clutch, then let it back out smoothly. The fly by wire system is just too senstive at 0 to just on throttle! On a recent trip from PDX to LA the problem was magnified by a sticking hill holder clutch. I am getting somewhat used to it but it is very annoying. Worse than my '72 fiat spider I had back in college.
  • Hi there

    I drive a 2008 black subaru forester manual base model.

    My car did the exact same thing all time and i asked the dealer what was going on.
    They were unsure at first and told me that they would contact subaru and get to the bottom of it.

    I recieved a phone call three days later saying that there was a Re-flash available
    I drove in the next day had the re-flash done and all was well.

    I read the report about disconnecting the battery on here and then the problem came back

    i found out that:


    Good work and thanks for the advice
  • "... contemplating buying a 2007 ForesterXT sports auto... I have read some disturbing things about a surging problem, at least in 2006 Foresters... traveling downhill..."

    I have a 2008 Forester automatic. I had read about the surging not long after I bought the car new. I did not notice it until I read about it and went looking for it. I can barely feel it when coasting at slow to moderate speed against a light throttle. I don't feel it with throttle off. But in a long downhill coast against a light throttle, the engine feels like it alternates between the light throttle and off throttle. Surging is too strong a word, and I don't see what could be disturbing about it. Go take a test drive and see if you can even find it.
  • ateixeiraateixeira Posts: 72,587
    I bet it's emissions related, something about the revs dropping too quickly.
  • There are no revs to drop. The engine is coasting down a long hill at steady rpm against a light throttle.
    That is, the throttle is less than what is needed to maintain the speed, and the engine is being pulled down the hill faster than the throttle.
    If you take your foot off the gas, the effect stops.
    I am never aware of it, and cannot feel it, unless I go to a place and make it happen. There is one long valley descent that I can hold 40 mph on, to feel it.
  • ateixeiraateixeira Posts: 72,587
    Is anything drawing lots of power from the alternator that might require more revs? Like A/C kicking on?

    Just brainstorming... :confuse:
  • It's winter here.
    And it is not more revs.
    That's why it is not a surge. The car is not changing speed.
    The engine alternates from coasting at idle, to coasting at closed throttle.
    Neither the engine speed or car speed changes.
    But you can feel the difference as the coasting alternates between free with some throttle, and drag with no throttle.

    To escape the situation, either take your foot off the gas and truly coast freely, or give the engine a little more throttle so it is not coasting agains the light throttle.
  • I recently started having a surging issue with my 2005 2.5i (non-turbo) Outback limited with automatic transmission and 64,000 miles.

    It seems to have started since I had an emissions related recall done in August.
    It happens at stop signs and lights, but was most noticeable last night in stop and go driving on the parkway (highway). Not sure if I was going downhill or not. The engine would surge up a little almost every time in between slowing down (almost to a stop) and starting back up. I am not comfortable with this as I am concerned that it may one day take it to the next level and slam me into the car ahead of me!
    Also, I don't know if it's related or not, but also since that recall, I have notice the transmission downshifting or jerking sometimes as I complete a stop.

    Are these symptoms the same as what you guys are talking about?

    I am probably going to make an appointment at the dealer about this.
  • "... I recently started having a surging issue... at stop signs and lights... Are these symptoms the same as what you guys are talking about?..."

    That is nothing like what I have, which does not concern me at all. When coasting against light throttle, my engine alternates between light gas and no gas, never getting more gas than I am giving it. It is the opposite of a surge.

    You have something else. It sounds like your engine gives itself gas, more gas than you are giving it with the throttle. Now that is a surge.
  • johnvjohnv Posts: 40
    I have the same (08 Forester PZEV) when coasting on light throttle. It is either on or off. Not a surge, but doesn't make for a smooth ride. I guess you just can't feather the gas like you can when its a physical wire to the throttle.
  • I really need some help figuring this out. I have 08 XT, auto, that was bought new and now have 52k miles. It periodically has this problem where it will cut out power and feel like it is missing or something. This typically happens while driving about 65 - 70 mph, and the rpms around 2200 - 2500. It generally happens while driving up a very slight incline of a hill (I drive 50 miles each way on this hilly hwy) I thought it was contaminated fuel initially and put fuel treatments in but that did not stop the problem then I had a tune up done by Firestone thinking I just needed new plugs but it is still doing it. Could this be my transmission possibly? I also noticed that when this happens the rps do not go down at all and thats why I think it may be the trans. Please help!
  • Just curious: what is/was your current mileage?
  • johnvjohnv Posts: 40
    I'm at about 13k miles. I had a reflash done to the ECM that solved a problem with the idle racing when the clutch was in. I haven't gone in for the WVN-24 ECM reflash, but for all I know it could be one and the same.

    I haven't particularly noticed the binary throttle issue since the reflash, but I'll try to remember to watch for it next time I'm on the downhill.
  • johnvjohnv Posts: 40
    The reflash seems to have made the throttle less blippy when coming on/off gas at low speeds (coasting up to a stop for example). I never had/noticed any problem at higher speeds (freeway, etc).
  • My Forester surges whenever the clutch is pushed in and you are coasting. It will pulse between 1000 and 2200 rpm but on occasion has gone over 3000 rpm. It stops surging when you come to a stop or if you move the shifter to the neutral position.
  • My 09 Forester X Premium 5-speed manual does the same exact thing. And the transition from off throttle to on throttle is practically impossible to modulate smoothly.

    Does anybody know the fix?

    Does it have anything to do with a too hot thermostat? It acts like it's running hot, but I can't tell because it has no guage. When it's still warming up, not totally up to full temp but not cold, it runs perfectly.
  • Took my Forester in again and they reprogrammed the ECU with an update and problem solved!
  • ateixeiraateixeira Posts: 72,587
    Glad to hear it.

    I was going to ask if yours is a PZEV, but it's a moot point now. PZEV will drop revs slowly for emissions purposes, but what you describe did not sound normal anyway.
This discussion has been closed.