2005 Subaru Impreza



February, 11, 2012 AT 3:48 AM

Two and a half years ago my fuel system got contaminated with ethanol and water. I ended up replacing the entire fuel system, including the engine, over the next two years. Little by little, performance was restored. Apparently the ethanol that got loose damage everything it touched, to some degree, but there is still a problem. It's still quite slow off the pedal, and the engine takes forever to warm up. Subaru's are normally very responsive when you hit the gas. I've been driving them for 11 years so I know exactly how tight they are off the gas.

An important factor in that whole catastrophe was the fact that I had to push on the pedal pretty far to get my car going and keep it going. To get it to go cruising speed on the highway, I had to nearly floor it. After I replaced the fuel filter, much better, but not completely better. So that's when I began replacing the fuel system.

Something else interesting is the fact that when I start the car, I will hear swishing or bubbling in the gas tank for a few seconds. Perhaps gas is being returned to the tank after not meeting enough air at the engine.

The seven or so shops I have taken this car to all think the car runs fine. My primary shop - local Subaru dealer - even thought it ran fine back when the fuel was diluted and going super slow. But I'm the one that's driven it for 92k miles. The catastrophe happened at 70k. It is definitely not fine. I bought this car for the speed, and now it’s slower than the car I replaced it for.

SInce replacing the whole fuel system, lately I've been taking shots in the dark with the throttle system. I replaced the throttle body/position sensor. That made the pedal a little more responsive. But the core problem is still there. I also replaced the front oxygen sensor, throttle relay, MAP sensor, and MAF sensor. The car does not have an idle air control valve. Subaru stopped using those in the Impreza in 2004, so they say.

I thought there might have been a vacuum leak, but I had that tested and they detected no problem.

It's like something is inhibiting air flow to the engine, or just plain not opening the throttle enough. Could something have been pushed out of calibration? ECM perhaps? Maybe something just before or just after the throttle body got trashed? Could the air intake boot have a problem that didn't show up on the vacuum test?


4 Answers



February, 11, 2012 AT 4:00 AM

After 2 years, all that is gone plus you replaced everything.

The one thing you never talked about was the cat converters. They do not react well to ethanol and could be causing a restriction directly effecting performance. I would start there.




February, 11, 2012 AT 10:25 PM

I actually did replace the cat converter to no avail, but it's interesting you mention they react with ethanol. No other mechanics I have been to (at least 7) mentioned that. Is there something else along the exhaust system that could be damaged? Is it possible the exhaust system minus the cat converter needs to be replaced?

I also had to replace the transmission. I also replaced the timing belt as that was due somewhat soon anyway. They found leaking headgaskets when they went to replace the belt, so that had to be fixed too. I strongly suspect that problem was caused by this problem. My '94 Legacy didn't have leaky headgaskets until 175k miles or so.



February, 11, 2012 AT 11:47 PM

No other exhaust parts would be effected here.

No offense, but you are blaming way too much on the ethanol issue. A lot of time has gone by and the effects are long gone. Head gaskets would have nothing to do with that. That is a common issue with subarus. We have done tons of them for that kind of leak.

The fuel system has no more contamination and besides, it all went away weeks after the incident. You said you replaced the motor so all the residuals are definitely gone.

I would start with basics like a compression test. The fuel pressure, once again is critical. Spark as well. The timing belt should be re verifed to insure that you are getting all the power you want.

I think a shop familiar with subarus would be your answer to adress your concerns and get you a good answer.




February, 12, 2012 AT 2:02 AM

I understand the ethanol/water and residue thereof were gone a long time ago. Something got damaged or completely trashed because of them, or perhaps something got worn out due to the fact that I had to ram hard on the throttle to keep the car going when the contaminants were there.

I did the engine compression test. Spark plugs were replaced when my Subaru shop first took it in.

Now that you mention it, I don't think I ever had the fuel pressure tested. I'll check on that soon. If is low, do you think the ground wire and connection for the fuel pump could be warped or something?

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