Mechanics

ENGINE REVVING SLIGHTLY HIGHER

2005 Subaru Impreza

Engine Performance problem
2005 Subaru Impreza 4 cyl All Wheel Drive Automatic 72000 miles

I actually submitted this problem to someone a few months ago, with no success. So if this looks familiar to you, that’s why…

My car is revving slightly higher than it used to, and it’s experiencing some sort of backflow or bubbling in the gas tank at start up. This latter part is very brief at start up, when it’s cold.

Long story short, water got in my fuel system last summer. My car lost significant power, but it turned out there was another factor contributing to the lost power as well. The primary problem was water in my fuel filter, so I had my dealer change that out (they had to replace the filter and pump, as they are housed in the same assembly). Power was almost completely restored but the engine was still revving a little higher than it was before.

I thought there might have been a little water left in my fuel system somewhere, so I dumped a bottle of dry gas (Heet) in there. That didn’t do anything, so next time I used 2 or 3 bottles. Right after doing so, I shot over to the gas station to fill up. It was upon starting the car after this fuel up that the funny backflow/squishing/bubbling sound started. There was also no improvement in power.

Later I found out the battery was dying, and that was another contributor to the lost power. So that was changed, and I believe some power was restored, but the engine is still revving higher.

Around a month ago I had the Subaru dealer drain the fuel system. I know they drained the tank and line. Is there fuel sitting in the engine or other parts when it’s off? Could they have missed it?

This week I changed out the fuel pressure regulator, just taking another shot in the dark. Just about no change in performance. It’s like the Heet is taking up space in my engine and not burning off. Does it sound like the Heet is stuck in the engine, or fuel system, somewhere?

I have $35 more for the solution.
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Tonoklein
April 9, 2010.



Hi tonoklein,

I checked through what had transpired previously and would like to know what system criteria had been done for your vehicle, H4DOTC, H4SO U5, H4SO or H6DO?

Is it with 4speed or 5 speed AT?

The higher rpm, is it occurring at cruising as well? If yes, it could be the the lockup is not working correctly. Did you ever try to retrieve for trouble codes and was any found?

KHLow2008
Apr 11, 2010.
I looked all over the car and owner's manual for anything that starts with H4 and came up empty. Where would I find such? I'm going to try and dig up the manufacturer sticker that was on the window when I bought the car. I think I still have it.

It's a 4 speed AT.

Yes, the higher rpm occurs at cruising. It's constant.

I took the car to the dealer when this first happened and they gave it a diagnostics test. It came up with no codes, even with the water in the system.

Do you have any idea what could be causing a swishing/gargling/bubbling sound in the gas tank at start up? Does fuel sit in the engine or other parts when the ignition is off?

Tiny
Tonoklein
Apr 12, 2010.
Sorry for the error on the H4 thing. I have edited the post.

The swishing and bubbling noise in gas tank at start up is most probably the evap system in operations so should be nothing to worry about.

Whe ignition is off, the fuel line from fuel pump to the fuel rails would have fuel in it. At inititial igntion ON, the fuel pump would prime the system to get the fuel pressure up.

Though no trouble codes have been retrieved, I believe the higher rpm at given speed is most likely due to the lock up clutch not locking in.

KHLow2008
Apr 13, 2010.
I talked to a couple reps at the dealer and they both said that a busted lock up clutch would certainly trigger the check engine light.

It seems like some part may have met the end of its life due to all the extra RPM's the engine had to make to keep the car going when the water problem started. Could the timing belt be off?

Tiny
Tonoklein
Apr 29, 2010.
If the timing belt is off, it would not result in the extra rpm. You would have performance related issues.

For the lockup issues, it would normally trigger a code but at times when electrical system are working correctly with a slight slip due to hydraulic pressure leakages, codes might not be triggered.

KHLow2008
Apr 29, 2010.
My dealer just explained to me the lock up clutch and when it engages (after the highest gear is shifted). It doesn't sound like my problem. My problem is at the acceleration level and on up to the cruise level. It actually feels like a loss of horsepower.

Back when I got in a front end collision with my Legacy, the collision shop did something to increase the horsepower more than it was producing before the accident. Is there something you can tweak or replace to increase horsepower output?

Tiny
Tonoklein
May 4, 2010.
For increas of power, there are many ways to go about and the increase would depend on what had been carried out.

It can be a simple add on such as the air filter for a faster air flow which increases the acceleration slightly, replacing the exhaust manifold to tweaking the Engine Control Unit, (computer).

KHLow2008
May 5, 2010.