Hey everyone! I just bought a WRX three days ago- a blue 2004 wagon that is bone stock and appears to have been very well taken care of. After driving it a few days, though, I am left with a couple of questions.

When I test drove the car it felt great. I purchased it the next day, and the dealer filled it up for me. I noticed that at around 4-5000 rpm the boost levels would fluctuate up and down, some hesitation would occur, and I would hear an audible "tick" whenever the levels began to momentarily drop. I ran the tank to empty, filled it up with premium, and it has been running great ever since. Do you think the dealer just put the wrong grade of gas in it? Have any of you put lower octane gas in the car by accident and experienced similar results?

My next issue is as follows. After the above episode, I began to watch the boost gauge carefully. The car now pulls strong through every gear, but I have noticed that boost begins to dop off slightly between @ 6000 and 7000 RPM. The car's ECU is programmed to lower boost levels slightly before redline, right? Just wanted to make sure.

Thanks in advance for your input.

Welcome to the club! :D

The turbo in the Subaru will pick up around the 3000rpm mark and start to drop off around the 5500rpm mark - it's more to do with the size of the turbo in the car. (smaller turbo = low end boost, larger turbo = higher end boost).
It's nothing to do with the ECU so much as the size of the compressor.

BTW, if you have the 'factory' boost gauge, don't trust it too religously - I have one and found it can almost be outright sporadic. It doesn't really measure boost anyway so much as vacuum line pressure - have a look where it ties into the pipes under the hood and you'll see what I mean.

Yes, sounds like the dealer put the wrong grade of gas in - dumbass dealer!

Welcome to the board! As an entry fee, we require pictures of your ride. :-)

Thanks for the welcome! Yes- dealers can be pretty retarded sometimes. They were good to work with, though, so its hard for me to get too mad. I suppose no damage was done. (At least, I hope. It seems to running great now.) I'll try and get some pics of the car on here within the next couple of days. It's nothing too special though- just a wr blue wagon with the stock 16 inch wheels. Maybe some BBS RK or ASA AR1 wheels are in the near future...:grinyes:

BBS RK or ASA AR1 Those are "nice," ;) but check out the BBS RE - those are the JDM Subaru hotness! :D

welcome to the scooby club

I just wanted to mention that those ECUs protect the engine pretty well when the wrong gas goes in. i've heard they also go nito limp mode when things totoally get screwed.

and yes, the boost tapers off after about 6K. Easy enough fix is to get a bigger turbo without increasing the boost too much and it will pull till redline. e.g. VF34.

Hey sounds like you got some knock going on. I think the dealership probably put in cheap gas for you, make sure to always run premium, 93 and if 93 i snot available use whatever is the highest. IF you use cheap gas the car will burn the fuel weird I forget what knock or detenation really is, but search on i-club.com or nasioc.com.


(I can't believe my AF name and pw actually worked after all these years)

Thanks for the info. It's been a little while since I purchased it, and the cause was the wrong grade of gas. I ran it to empty, filled it back up with 93, reset the ECU, and everything was great. I just finished doing the 60K service myself, and it is running better than ever. Couldn't be happier.

I guess it's about time to change to change my avatar and sig, isn't it?

^ lol, i would say so. but still have a little "tribute" to the Z (those are sweet cars.). Oh, and congrats on the car. Cant wait for pics.

That ticking noise you heard is detonation, which you should listen for if you plan on modifying the car at all. detonation is when you get combustion while the piston is still going up and can end up being very costly. That's why you put premium gas in, instead of regular. premium has a higher octane which has a higher resistance to combustion. You may have already knew this, but at least this might help somebody :p