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Forester faulters-changed everything but the body

19 messages,  Last post on Feb 02, 2011 at 5:02 PM

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What is this discussion about? Subaru Forester

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#1 of 19 Forester faulters-changed everything but the body by mickinik

Jan 27, 2011 (3:12 pm)

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)

#2 of 19 Re: Forester faulters-changed everything but the body [mickinik] by aatherton

Jan 28, 2011 (7:04 am)

Replying to: mickinik (Jan 27, 2011 3:12 pm)
Have the fuel injection pump and injectors checked next.

#3 of 19 Re: Forester faulters-changed everything but the body [aatherton] by mickinik

Jan 28, 2011 (8:37 am)

Replying to: aatherton (Jan 28, 2011 7:04 am)
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?

#4 of 19 Re: Forester faulters-changed everything but the body [mickinik] by xwesx

Jan 28, 2011 (9:52 am)

Replying to: mickinik (Jan 28, 2011 8:37 am)
Does it have any problems without the transmission engaged?

#5 of 19 Re: Forester faulters-changed everything but the body [mickinik] by aatherton

Jan 28, 2011 (12:35 pm)

Replying to: mickinik (Jan 28, 2011 8:37 am)
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?

#6 of 19 Re: Forester faulters-changed everything but the body [xwesx] by mickinik

Jan 28, 2011 (2:18 pm)

Replying to: xwesx (Jan 28, 2011 9:52 am)
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.

#7 of 19 Re: Forester faulters-changed everything but the body [mickinik] by xwesx

Jan 28, 2011 (2:34 pm)

Replying to: mickinik (Jan 28, 2011 2:18 pm)
I think the torque converter is toast (and getting worse).

#8 of 19 Re: Forester faulters-changed everything but the body [aatherton] by paisan

Jan 28, 2011 (3:04 pm)

Replying to: aatherton (Jan 28, 2011 12:35 pm)
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

#9 of 19 Re: Forester faulters-changed everything but the body [xwesx] by mickinik

Jan 28, 2011 (3:46 pm)

Replying to: xwesx (Jan 28, 2011 2:34 pm)
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)

#10 of 19 Re: Forester faulters-changed everything but the body [paisan] by mickinik

Jan 28, 2011 (4:17 pm)

Replying to: paisan (Jan 28, 2011 3:04 pm)
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?????

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