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Forester faulters-changed everything but the body

mickinikmickinik Posts: 10
edited September 12 in Subaru
Help!! I have a 2002 2.5L Forester. Car starts and idles normally. Mostly when v-cold (20-30 deg), the car will drive normally for 5 minutes. Then when you start giving gas slowly car will normally accel to approx 2000 rpm, then as you slowly add more gas, car will slow down. If you push it farther to the floor, the car will quickly accelerate and drive like it would with the pedal down. If I take my foot off the gas and slowly reapply it, the car will bog again. (If I can get it to happen in the garage, adding carb cleaner to the intake makes it rev up). Replaced: fuel pump & filter, cam & crank sensors,engine&trans computers, Throttle pos sensor, MAP/temp sensor, atmospheric press sensor, plugs, wires, coil, (fuel press tested OK during problem). During warmer months, and even now when its warmed, the car can run normal except for occasional loss of power during cruise. -OR NOT! (no CEL-other than a miss if I let the thing buck too long)

Comments

  • aathertonaatherton Posts: 617
    edited January 2011
    Have the fuel injection pump and injectors checked next.
  • mickinikmickinik Posts: 10
    edited January 2011
    replaced the fuelpump and all filters. Observed the fuel pressure during the problem and it remained normal. Disconnected each injector and that cyl would miss. reconnect and engine would smooth out. When I have the problem, I don't have 1 miss, the whole engine looses power. Last night (25 deg outside) car took off normally for approx 2minutes. then got so weak that it almost wouldn't take off from a stop. When I got it going car had power, but if I would come back on the accelerator and slowly apply power again, car would slow down. I disconnected the IAC thinking maybe it was shorting the computer and car had same symptoms. I also monitored the 5 volts off the computer (an earlier check)and that remains normal. I have replaced the TPS and also ran the car with the TPS disconnected and I still had the problem. When I parked it, I put it in gear w/break on and pressed accelerator slowly. Engine would rev to1500-2000rpm, then start dropping back to 500rpm. if I continued to press down accel, car would eventually jump up to 2000+RPM and have power. I noticed that when RPM is dropping down below 1500, if I let up on the accel, back around 1500 RPM the car gets normal power - if I press down again, engine weakens again
    I'm wondering if any of the speed sensors in the transmission cause the trans computer to send a "retard" signal to the engine computer?
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,508
    Does it have any problems without the transmission engaged?
  • aathertonaatherton Posts: 617
    edited January 2011
    You replaced the fuel pump in the tank. I suggested checking the fuel injection pump on the engine.

    I think the ECU is programmed with a timing advance curve, which is the modified by "retard" signals from the knock sensor, which are then learned or mapped so that ECU knows not to keep advancing into knock territory.

    I don't think the transmission has any timing input to the ECU at all.

    I would think that your bogging or hesitation problem would result in a diagnostic trouble code (DTC) that would cause the check engine light (CEL) to come on. Then you could use a code reader and get some idea of where the problem was. Do you have no CEL and no DTC?
  • mickinikmickinik Posts: 10
    edited January 2011
    When I'm in park or neutral the car will rev right up.
    I have to load it up in gear to see the problem. It started as an occasional loss of power while I was driving it. If I would press the pedal down, the car would come right out of it and have normal power. This went on for several months and I couldn't repeat the problem in the garage. Now the problem is more severe (I think because of the cold weather, as a matter of fact, I could let the car warmup for 20 minutes and I MAY NOT see the problem. When I'm driving, after awhile the problem seems to go away)
    I do get a check engine light-only if I let the car buck for an extended period of time - the code is for a missfire in one of the cylinders-changes between cyl. I changed plugs, wires & coil,compression good & even
    I did change the Knock sensor and ran the car with it disconnected with no change of symptoms.
    I'm not sure what you mean about the fuel pump this is a gas engine and I maintain proper pressure at the injectors.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,508
    I think the torque converter is toast (and getting worse).
  • paisanpaisan Posts: 21,181
    You replaced the fuel pump in the tank. I suggested checking the fuel injection pump on the engine.

    Have you ever worked on a Subaru? Obviously not, because they don't have fuel injection pumps. They have a fuel pump in the tank and fuel injectors for each cylinder.

    I don't think the transmission has any timing input to the ECU at all.

    The ECU does get data from the 4EAT, actually from the TCU. Heck on my '92 SVX the 4EAT TCU actually had the ECU turn off 3 cylinder's fuel injectors on downshifts to make it smoother.

    I would think that your bogging or hesitation problem would result in a diagnostic trouble code (DTC) that would cause the check engine light (CEL) to come on. Then you could use a code reader and get some idea of where the problem was. Do you have no CEL and no DTC?

    You won't get a DTC/CEL necessarily from just bogging down. Only if you get an actual misfire or a bad reading from a sensor.

    Have you checked your timing belt/timing? You could have jumped a tooth and under heavy acceleration this may be causing an issue. Also how many miles on the current belt?

    -mike
    Subaru Guru and Track Instructor
  • I don't think it's the torque comverter because When I can get the car to have the problem in the garage (in gear and slightly trying to rev the engine) While it's stumbling, I can spray either across the intake and get the car ot rev up normally.
    I installed timing belts on this car about 2 years ago (approx 20,000 miles ago)
  • I was never in these forums before so I may be messed up with my replies.
    Mike, I think I am going to disconnect the trans computer when I have the problem in the garage and see if that makes a difference. From what i understand, the trans has speed sensors that monitor the front drive and rear drive. If thev aren't equal (a wheel is spinning) the trans computer sends a retard signal to the engine to weaken it until the slipping stops.
    Possible?????
  • paisanpaisan Posts: 21,181
    Definitely a possibility of that being the issue. Disconnecting it may not fix it but if it does then you will have narrowed it down.

    -mike
    Subaru Guru and Track Instructor
  • aathertonaatherton Posts: 617
    edited January 2011
    "... I'm not sure what you mean about the fuel pump this is a gas engine and I maintain proper pressure at the injectors."

    I had thought there was a separate higher pressure pump for the injectors, maybe because I used to have a diesel Rabbit.
    But I now understand that the fuel pump in the tank is the only one for a gas engine, and you said yours is providing proper pressure to the injectors.
  • Sorry, I forgot to mention that this is a gas engine and it only has the pump in the fuel tank. You're right about diesel's thou, they have 2.
    I put the car in a heated garage today to work on it. Didn't get to do anything on it, but when I drove it to the (30 deg) garage, it was running so bad, I took side streets incase it stopped. When I left the garage and the vechile was warm (60 deg). It ran rather normal ( although when I blocked the wheels and put it in gear before I left the garage, the car would bog down and I actually had it floored and it wouldn't build power) - I did notice that if I sprayed starting fluid across the intake, the car would surge forward. Definately a gas problem. I took all the injectors out and inspected the screens at their inlet and they all looked v-clean
  • aathertonaatherton Posts: 617
    "... this is a gas engine and it only has the pump in the fuel tank. You're right about diesel's thou, they have 2. "

    In addition to a diesel Rabbit with a pump for its injectors, I also had two BMW 2002s, and remember that the 2002tii had a separate mechanical fuel injection pump (Kugelfischer), and I thought perhaps the old Rochester fuel injection system for Corvettes had its own pump.
    I did not realize that modern fuel injection systems only needed one pump in the tank.
  • paisanpaisan Posts: 21,181
    I put the car in a heated garage today to work on it. Didn't get to do anything on it, but when I drove it to the (30 deg) garage, it was running so bad, I took side streets incase it stopped. When I left the garage and the vechile was warm (60 deg). It ran rather normal ( although when I blocked the wheels and put it in gear before I left the garage, the car would bog down and I actually had it floored and it wouldn't build power) - I did notice that if I sprayed starting fluid across the intake, the car would surge forward. Definately a gas problem. I took all the injectors out and inspected the screens at their inlet and they all looked v-clean

    I'm thinking it's a vaccum leak, MAF/MAP, or Coolant Temp Sensor issue. I would lean toward the first 2 before the coolant temp sensor.

    -mike
    Subaru Guru and Track Instructor
  • I will check the vaccum again while i'm having the problem. I did install a new combonation intake manufold pressure/temp sensor into the intake a few weeks back, but saw no difference
  • I will check the vaccum again while i'm having the problem. I did install a new combination intake manifold pressure/temp sensor into the intake a few weeks back, but saw no difference
  • unplugged the trans computer, put the car in gear and with light/medium acceleration, still had the problem. - RPM rose smoothly to 2000rpm and then fell back to 500rpm kicking and sputtering as I continued to accelerate.
    I pulled the timing belt cover and everything looked good, (installed 40,000 highway miles ago). good belt, tight, timing marks aligned, no loose, bent or chipped pulleys. cam sensor (which was replaced) looked tight and positioned correctly.
  • Same problem with the trans in neut or park. A little harder to notice without the load on it, but I can make it happen
This discussion has been closed.