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2002 forester
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Hi. I have a 2002 Forester X. Recently I took the car to the dealer to find out what my check engine light was trying to tell me. The code was for the K.S. I replaced the knock sensor and fuel filter myself after having the car 'buck' on me for a few days. Check engine light went out but the 'bucking' persisted with no C.E. light on. I then changed the spark plugs and did a compression test. (#4 was lower than the rest.) Still 'bucking'. Changed the spark plug wires, the bucking went away for half a day, but came back. I just changed out the post-catalytic converter O2 sensor after a REALLY awful drive to my garage. (bucking really violently, and not allowing the engine RPMs up) Things were great for a day, but just now it did it again driving about 25kms/15 miles away from home. It seemed to settle, but I arrived at my destination before I could get a good opinion of it settling down. Also, the C.E. light came back on during this drive...
I am at the end of my patience around this. I would like to avoid the $60 for the dealer to read the code, but I am leaning that way..and btw the OBD2 reader I borrowed, brings back an error message when I connect it. I was thinking computer problem. What the hell else could be leaning out my engine when it has sooo many new parts?

Help! Please!!
 

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2007 FSTI and X 6 MT
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22,252 Posts
Welcome. Since this is your 1st post I will attempt to help you out. From what I know about cars is that throwing parts at them ususally does not fix the problem. I would have had the subaru dealer fix the problem from the start and called it a day. If they could not fix it, then its on them.
 

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2008 LL Bean (4EAT)
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4,784 Posts
... I replaced the knock sensor and fuel filter myself after having the car 'buck' on me for a few days... but the 'bucking' persisted with no C.E. light on. I then changed the spark plugs... Still 'bucking'... a REALLY awful drive to my garage. (bucking really violently, and not allowing the engine RPMs up)... just now it did it again... What the hell else could be leaning out my engine when it has sooo many new parts?...
Bucking is a cutting out, a misfire. Your continued bucking reminds me of what happened to our car a year ago.

After a fill up it suddenly would barely run. It misfired, cut out, bucked and made no power. We limped 20 miles to home and had the car towed to a shop. The shop found a lot of water in the gas. They gave us a gallon jug half filled with water and said that was only part of it. We called the gas station and they said they had a dozen other reports already and had shut that pump down. It cost $1000 to have our tank removed and the the fuel system cleaned. The gas station repaid us. They said a tank truck must have given them the water, and their water alarm system had not caught it.

It is possible you have water in the gas. It lays in the bottom of the tank, and sloshes around. Our car would run better when pointed uphill. Evidently that moved the water away from the fuel pump. You could have just a little water moving around on the bottom of your tank. Perhaps a few cans of "dry gas" (alcohol) additive would absorb the water and allow it to be burned off without bucking.
 

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2009 Forester X 4 A/T
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305 Posts
could also have a fuel pump on the blink
A distinct possibility, especially if the OP is a person who does not fill the gas tank, instead running a quarter tank or less and putting in $5 every other day or so.

Seriously- a local import shop asks everyone on whose car they replace a fuel pump how they normally fuel up. Fill-up to the top or just a few gallons. 80% of the failures are those who do the just a few gallons in the tank, which makes sense since the fuel cools the pump motor immersed in the tank.
 

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2010 Forester Premium
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7 Posts
I believe your engine is having trouble breathing. Your computer is basically trying to compensate for either too much fuel/ too little fuel/ too much oxygen/ too little oxygen. There are such things as a rich misfire and a lean misfire. Take it to the dealership and have them follow the diagnostic chart for that code. If not, find a diagnostic chart for that code and do all the tests (like a technician not a mechanic) and isolate the problem area.
 

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2008 LL Bean (4EAT)
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... Take it to the dealership and have them follow the diagnostic chart for that code. If not, find a diagnostic chart for that code and do all the tests...
Yes it could be the fuel pump, or the dealer could run diagnoses and tests.

But if it should be a little water in the tank, it would be cheaper to see if a couple of cans of dry-gas additive would absorb and disperse the water into the gas so it will burn without bucking. He would know almost immediately if this was going to work. If not, then he could go to the dealer.

As for the fuel pump being damaged by not keeping much gas in the tank, the pump is cooled by the gas it pumps through itself, regardless of how much gas is in the tank.
 
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