Slight loss of power, and significant MPG drop.

[WagonGuy]

Going stage 2 about a month ago went by the book. No issues, no problems, pure joy. I was even surprised to see how good the MPG numbers were. I constantly clocked the average MPG (using AP) at 28-30 highway and 22-24 city. At one point I got as high as 34 mpg.

Lately the weather has gone south with tons of rain and temps in the range of 40-55F. That's when I noticed something weird about how the engine performs. Mainly, it got hungry for fuel. I can literally watch the fuel gauge needle sink slowly as I drive. Last time I checked it with AP it barely pulled off 23 mpg on the highway staying completely out of boost with an average speed of 40 - 60 mph. The idle also got weird, instead of going all the way down to 650 rpm it hovers at about 1000 rpms for about 10 seconds the then slowly creeps down to a regular 650. The engine also sounds rougher, and there's a slightly noticeable drop in power before 1800 rpms. Once it gets past 1800 it seems to be back into a normal stage 2 torque feel. Another weirdo is how much more engine vibrations can be picked up from the pedals (clutch, brake) and the steering wheel. I'm not sure if that's related but I haven't noticed that before. To finish off the list of symptoms it backfires (pops) when letting off the gas, which has not happened before as bad as it is now.
I really don't know what to make out of all this. My wild guess for a quick fix would be to clean the MAF sensor, since I haven't done that in a while and I noticed that the K&N drop-in filter tends to dirty it quicker then the stock insert.
So to recap:
- lower then normal MPG
- slight hesitation below 1800 rpms
- loud exhaust pops
- high 1000 rpm idle for a moment
- excessive engine vibrations felt via pedals and steering wheel
- no boost loss, steady at about 15psi
- all fluids clean and at good levels
- no CEL

Mods:
- AccessPort stage 2 93 oct map
- turbo back exhaust
- gutted uppipe
- K&N drop-in filter


UPDATE:
I cleaned the MAF sensor, replaced the K&N filter with a new paper (FRAM) filter, flushed a stage 2 93 oct HGW map, did the Vishnu trick, and still not better. It just runs like a donkey, it jerks at lower RPMs, seems to be lacking power, it sounds weird, the smooth power band is gone, all together something is messed up. Ohh yeah, in order to reached stage 2 boost (16 psi) I reflashed a real time map from a regular stage 2 to HGW stage 2. This caused the max boost to drop from 15.1 before to 14.5 now.

[josnroh]

Maybe the winter blend fuels we have in the midwest with the additional ethanol?

[WagonGuy]

Maybe the winter blend fuels we have in the midwest with the additional ethanol?

This actually is a possibility and I thought about it as well. The sudden change from smooth stage 2 awesomeness to jerky, weird sounding crappiness was too sudden without any reason, I haven't done anything to the car to cause this. I had all fluids (coolant, and oil) changed at the 30,000 mile service interval about a month ago and the engine was smooth like silk. One day I start it up and it's like a 20 year old lawn mower. I guess I'll just drive like this until Spring or until something fails.

Would octane booster be a good thing to try to see if it's related to gasoline?

[WagonGuy]

UPDATE:

Got rid of all the symptoms.

Engine vibrations: that one was my mistake, I did the raised intercooler mod a while ago, and the new and longer passenger side bolt was touching the turbo heat shield. Adding few more spacers fixed it.

Low rpms hesitation and low MPGs were fixed by Seafoaming the crap out of it. Half a bottle in the tank, half a bottle in the vacuum lines.
I think the AICV cleanup is next on the list, as well as PCV valve checkup (slight oil deposit in the throttle body inlet).

In addition to that I also washed the engine bay and went through the Mother's 3 step paint polish and protection for winter. I think that was the biggest contributing factor in all this. My butt dyno detects many more bling HPs now.

After all this, the car is smooth now and gas millage improved slightly as well.

[josnroh]

Spit and polish did the trick.

[brfatal]

Damn, I would kill to get even the "bad" gas mileage you're getting. I don't even hit 20 hwy.

I wouldn't recommend using the AP's logging as fact. Measure your mileage at each refill.

[WagonGuy]

Spit and polish did the trick.

And it did it very well, I don't know if it's only in my head but everytime I wash and polish it, it feels like brand new and not just visually.

Damn, I would kill to get even the "bad" gas mileage you're getting. I don't even hit 20 hwy.

I wouldn't recommend using the AP's logging as fact. Measure your mileage at each refill.

I'm curious how the AP calculates the gas millage (injector flow?). The more I use it the more it feels like the instant gratification of knowing it right away may be giving me wrong readings.
Check out the picture below, it was on a sunny, warm (60F) day, after a 15 mile - 25 minute drive, mostly on the highway, with about 200-300 pounds of stuff in the car, when I was helping my brother move. And it pulled off almost 34 mpg, granted I was driving behind a moving truck at 55 mph.

[lytlec]

Seafoaming...Im searching this....what is it?!

[WagonGuy]

Seafoaming...Im searching this....what is it?!

It cleans up all engine carbon deposits, making it more responsive as well as temporary improves gas millage and butt dyno numbers.

Motor Treatment - Sea Foam

YouTube - seafoam in a 2003 WRX

[znn1337]

where do you put the seafoam

[wrxtreme06]

where do you put the seafoam

you should probably look at the links posted above.

[znn1337]

yeah I did but is it safe to take the vacuum line off the bpv? also should I put some in my oil/ gas tank