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Rough idle, exhaust tone is different!!

37K views 13 replies 6 participants last post by  turmic 
#1 ·
I just got back from changing my oil in my 04 WRX. While drive home I had an issue arise from my engine. I was driving it pretty spirited, and all of a sudden it starting running really rough, and was lacking power. The exhaust tone is really odd, sounds kinda like the timing is off or something. I have a strange suspicion that the timing belt skipped a tooth. My car has only 74k miles on it, and its ran perfect until this little issue. Its full of oil, and the turbo is spooling just fine...just runs strangely odd. The CEL light flashes indicating knock of some kind...however when it idles it doesn't knock or sound bad mechanically. only when I accelerate it vibrates very bad and just sounds really sick! Pretty odd considering it went from running perfect to this.....just wanted to get some feedback to see if anyone else has had the same issue....

BTW the CEL code doesn't say anything...just detecting knock..or timing off because of skipped tooth
 
#3 ·
Just throwing this out there (probably not the problem though)....

Did you just get a tank of gas?

B/c the other day I filled up and different station (not my usual) and my car started running like crap. It sounded different and just had no pep. I went through the laundry list of things (all those mentioned above) and nothing out of the normal. It turned out the gas was piss. I siphoned out as much as I could and filled up at my usual station....problem solved.

Here is my theory on why the gas was piss...

Less and less people are using 93 octane b/c of the bad economy and this was even worse due to the station being in a "less affluent area" (for those non PC people...it was in the ghetto and the price was cheap compared to by my house...LOL). Thus, the 93 is sititng in the tanks at the station MUCH longer than normal and the longer it sits the more the octane rating degrades. Either that or the bastard that owns that station is watering down his gas.
 
#5 · (Edited)
I changed my plugs at 60k....It is very unlikely that it is the plugs. I talked to a buddy of mine who is a reputable subaru tech in Colorado Springs. He recomended that I unplug that MAF and see if it changes. I did and nothing changed...after that I checked for a vaccum leak which I couldn't find any leaks. I'm kinda stumped.....I was thinking a leak of some kind because the sudden change in engine tone, thinking the maybe a hose popped off or something...it back fires pretty bad and just sounds so sick....its mind boggling

Also the subaru tech mentioned a compression test, so asked him if my engine doesn't have a knocking sound or doesn't smoke whats the likely hood my engine would be messed up. I also mentioned that the exhaust smells horrid kinda like being very rich. He said that I should check my plugs and see if one is fouled indicating an open injector possibly! I'm trying to get this figured out before I go and spend a bunch of money having someone else check it out when I can do most of it myself. Just hoping someone has seen a similar issue..thanky guys

Also I am Cobb AP stage 2 full TBE
 
#7 · (Edited)
Do a compression test and see what that tells you, I had a problem pretty close to this on my stock engine and it was the number 4 cylinder and after i took the engine apart i cracked my piston ring land. I would NOT be driving the car at all till you figure this problem out. Another thing to do is pull the ECU fuse or the fuel pump fuse so the car will not start then sit in your car and crank the car over for a little while to see if you can hear anything out of the ordinary while it is turning over. It should crank over smooth with no hick ups or anything. let us know man!!
 
#8 ·
I haven't done a compression test yet, because I don't have the tools atm to do so. However, I could go to my grandpas but I don't want to drive it over there

I pulled a fuse and cranked the engine for a bit, and everything sounded fine, I don't hear any strange noises or notice anything mechanically sounding odd....however, I think I have a broken motor mount or something because I hear a strange noise coming from the left side of the motor, which only makes the noise under load or when releasing the clutch from a stop.

Also, after driving around the block I finally got a P0304 code which would be cylinder 4 missfire....I'm really leaning toward fuel injector because of the really rich exhaust smell..also having new plugs and the coil packs seemed ok at the time....I'm not sure exactly though
 
#9 ·
You really need to do a compression test the only tools you will need is to take the plug out! I'm really going to lean to your number 4 piston is broke or something like that. Like i said above the number 4 is pron to break and they link it back to it receives less oil than other parts of the engine does. You really need to do that compression test and let us know.
 
#10 ·
Ok finally got the compression test done. Everything looks good as far as that goes.....130psi on all cylinders. When I pulled the plug on #4 I noticed that it was rather loose so I'm wondering if thats could be a possiblity of a missfire. the blug was fouled showing that the cylinder was dead. Other than that, I'm leaning to a bad coil pack....any thoughts?
 
#13 ·
So I went and swapped my coil packs around.. here is what I found out 1. My #4 cylinder spark plug was not snug, came out pretty easily. 2. The wire on #4 cylinder Coil pack seemed kinda loose also.

After swapping coils around and changing the plug. I went to start the car thinking I would get a misfire on #3 cylinder where I swapped the coils and to my suprise.....my car was running smooth with no misfire. Been driving it all day with no issues and it runs just fine. I'm guessing that the loose plug and wire were causing the miss, as everything seems to be normal now! Thanks for your guys suggestions. I'm thankful my car is fine :)
 
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