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Fuel Smell from the exhaust

19K views 34 replies 8 participants last post by  teflon_jones 
#1 ·
Hi... I'm brand new to the forum and brand new to Subaru as well. I recently got a used 2004 Impreza WRX in Texas, moved to Colorado the day of purchase (long story...), and am currently experiencing a very strong fuel smell from the exhaust, and fuel economy is suffering. I do not smell any fuel in the engine area. No parts have been changed, and no mods since purchase. I am brand new to the "mods" concept.

It also seems that the car is a bit sluggish on initial acceleration.



MODS -- I honestly do not know. I wasn't told of any engine modifications, but the car does have a scoop on the hood. I can post a pic of the engine area later this morning if that would help.

GAS -- Sorry to say that finances don't allow more than Regular Unleaded (87 Octane I believe?)

MILES -- 78000

I haven't done anything yet to try to fix this problem, however, I would prefer to work on it myself if there are some general things I can try before taking it in. I enjoy working on my Jeep, but I'm no auto mechanic. I can follow instructions, though! Is there any chance the change in altitude has anything to do with this? And if so... would it have been immediate or could it have taken some time to develop?

Thanks in advance for any help or advice!!
Tracy
 
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#2 ·
Whoa whoa whoa....

First stop using 87 octane. It costs like $2 more to run 93 octane and these motors need it. You're asking for problems if you continue running 87 octane and it is probably sluggish because of this. You probably have mad knock.
 
#3 ·
+80 bajillion. i know times are tough but if you honestly cant afford the extra few dollars you must sell your car and buy one that runs regular or find another means of transportation. we cannot use 87 octane

if youre not sure of what mods the car has you should have a knowledgeable subaru mechanic look over the car. if you have a true WRX, the hood scoop is stock. if you have an impreza, the hood was probably swapped with a wrx hood
 
#6 ·
93 Octane fuel is only 5-10% more expensive than 87 octane. On a typical $50 fill-up, that's half of a tip at a nice dinner. If you drive 10K miles a year averaging 22mpg, you're only spending approx. $115 extra in gas from 93 octane PER YEAR. $115 is certainly much cheaper than the $5K+ you'll spend in an engine rebuild when your motor inevitably toasts a piston ring.
 
#7 ·
Ok... I am more than open to the gas change. I simply have to admit to ignorance. It's what I've always used, but for certain, I've never owned a car similar to this! And the dealership was nice enough to sell it to us without an owner's manual, which we didn't realize until we were states away!

So... I have a 1/4 tank of this gas left. Should I fill it up with high octane gas before driving further? Or should I drive to almost empty before refueling?

Also, is there any additive that I can use at this point to further help the situation I've caused? Would the Chevron Techron that I've read about be of benefit?

Lastly... is it completely plausible that the choice of gas is the sole cause of the problems at this point?

Further info: I cannot find anything in the engine area to tell me if there are any mods; exhaust says "STI"; I don't know enough to say if it is a catless downpipe but I am trying to educate myself; rear of car says Impreza WRX. I believe a search of the VIN also lists the car as a WRX, not a WRX STI. I will work on posting photo from under hood...
 
#9 ·
You should refill now. You will increase the effective octane of the fuel to safer levels.

Please take a picture of the engine bay, and specifically the rear left of the engine bay and post it here.
 
#8 ·
I would start fueling up with 93 as soon as possible and drive the car really easy on this tank. I wouldn't use any additives. Just take it easy on this next tank. Definitely post pictures of the engine bay and anything else you have questions about.

You can get the Subaru owners manual here:

Subaru Owner Resource Center | My Subaru
 
#35 ·
I would start fueling up with 93 as soon as possible and drive the car really easy on this tank. I wouldn't use any additives. Just take it easy on this next tank. Definitely post pictures of the engine bay and anything else you have questions about.
Octane boosters only add about a tenth of a point of octane anyway so they're pretty much useless.

Unfortunately, not much. I believe I looked at a free Carfax report prior to purchase and didn't see any accidents or anything alarming. I want to say there were 2 previous owners. One of them didn't put hardly any miles on it, and the other did. I don't recall any other specifics, though.
Carfax is only worthwhile if it DOES show something. If it shows nothing, it doesn't mean the car is "clean." I had a Porsche I did $30k in damage to when I was younger and more stupid and the car still had a clean carfax.

Furthermore, the "sluggish" feeling of the car is likely the ECU learning the low octane 87 fuel. Likely it is pulling boost and adding timing to protect against detonation. I would fill the car with 93 IMMEDIATELY, then pull the battery leads and step on the brakes for 10 seconds. Then reconnect the battery leads. Your ECU should relearn the new fuel curve quickly.
Even without disconnecting the leads the car will learn the new fuel pretty quickly, though the more aggressive you drive (which you don't really want to do), the faster it learns. Once you burn through this tank of gas you'll be fine. In fact if you filled up 3/4 wit 91 and had 87 in there you're effective octane is probably still about 90 which is a little low but WAY better than 87!

I'll fill up with the best gas I can find, and follow your suggestions with the battery leads afterward!!
What do you mean by "best gas"?

Ok... I thought asking where I could find 93 Octane was a stupid question... but I'm thinking it might not be. Any advice on where to go in Aurora, Colorado to find 93?
The standard octane in CO is 91. I've lived here over 4 years and I don't think I've ever seen more than 91 anywhere other than the track or some isolated stations where you can get ~100 octane.

The car requires "premium" fuel and 91 octane qualifies as premium. There's absolutely no need to look for 93.
 
#12 ·
Very stock.
 
#15 ·
Do you just smell gas when the car is warming up? This may be normal as the car is in warm-up fuel enrichment mode. Is the car a manual or automatic? If an automatic, it will be sluggish regardless off the line. Keep in mind that a Kia Rio will have more off-the-line torque compared to this low-displacement, low-compression motor with a large exhaust restriction (turbo).
 
#16 ·
Incorrect!

That swaybar is not stock.:) Also I don't recall the tubs being blue on that model year. Either that or my age is catch up with me. (EDIT: Apparently I am going blind. Those are just covers. Ignore me like everyone else does.)

If you are down to 1/4 tank I would probably just fill up with 93 octane and drive it easy until your next fill up. That should take care of the issue with poor performance.

The exhaust smell may be from a possible exhaust upgrade that was brought back to stock, and installed poorly. Maybe without a gasket?

I would get that checked out though. Other than that I guarantee you will love your car as you become more educated about it.

You have come to the right place though!
 
#17 ·
Incorrect!

That swaybar is not stock.:) Also I don't recall the tubs being blue on that model year.
You are both smartasses.... I was talking specifically about the DOWNPIPE. I can't see the rest of the car ;)

Besides that's a strut tower bar, not a swaybar. The hydraulic lines were blue from the factory on the 2004-2005.
 
#24 ·
Ok, I can see where simply comparing to the drawings won't tell me... based on photos online. But... if there is a way to look under the hood and make this determination, I'd be interested in knowing it!!

Thank you all for the input/knowledge so far! I hope that I am able to continue learning more and more. Would love to make some "real mods" in the future.
 
#26 · (Edited)
If the previous owner did a 2.5L hybrid build, there would be no way to tell short of pulling the block and checking the code... or you can put your foot down and easily tell the difference ;).

Simply put, there was only ONE engine option available for the 2004 WRX, and that's the EJ205. The EJ257 was the STi motor, and this is clearly not an EJ257. Here are notable differences between the later EJ255 and the EJ205:
Engine Vehicle Auto part Car Fuel line


EDIT: At some point the fuel filter was moved to the fuel pump location... I thought this was in 2004? Are you sure this is a 2004?

Furthermore, the "sluggish" feeling of the car is likely the ECU learning the low octane 87 fuel. Likely it is pulling boost and adding timing to protect against detonation. I would fill the car with 93 IMMEDIATELY, then pull the battery leads and step on the brakes for 10 seconds. Then reconnect the battery leads. Your ECU should relearn the new fuel curve quickly.
 
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