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04 Forester XT Manual
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Discussion Starter · #1 · (Edited)
Ok, I will prequel this with the engine has been rebuilt recently, It has maybe 3500 miles on it so far. head rebuild, honed, new rings, new bearings, all new exhaust valves. Engine built built by my wife observed/helped by me when necessary.

This is also new since the rebuild, and NEVER happens under full load.

The issue that I'm noticing seems to be a skip, BUT it's a pretty violent one. Almost like it's more than one cylinder. The ONLY thing that I've been able to relate to this issue unfortunately is it has done it when it snows. This is my wife's car and I'm posting on her behalf, it's happened to her many times because she's typically the one driving it when it's snowing... I've driven the car many times as well and have been in it many times when she's driving it... I've felt this "Skip" once and it was when it was lightly snowing.

Yeah I know really! does snow have to do with anything... I'm thinking the same damn thing, It hasn't done it simply due to the extremely cold temps either which is very odd. I did start the car recently after the last big snow storm to clean it off and it smelt like fuel bad and upon inspection I found one fuel injector o-ring that I damaged when I was re-assembling the motor (Cylinder #3), Swapped that out and I was HOPING and thinking maybe I found the issue but I felt the skip a day later as well as today on her ride into work when it was snowing very lightly the skip happened a few times.

Unfortunately I have not been scanning it when this happens so I do not know if it registers as cylinder roughness or on which cylinder if it does. This is my next step to do so I have more direction but I was just throwing this out there to see if anyone has any ideas on what could be going on. I scanned the car last night on our way home from Gregg's in North Kingstown to Plainfield CT and the whole ride it only registered one "misfire" on cylinder 2 but I never felt it.

Mods
Perrin Catless up pipe
CNT catted downpipe
Cobb Catback
GFB Respons BOV
07 Legacy Oil pan
KillerB oil pickup
Previous owner removed air box chamber that's in the fender well the rest of box is still intact.

FWIW I have NOT replaced ANY of the sensors on this engine since I purchased it and it currently has 107k miles on it. I do not know if anything was replaced prior to me owning it though.

Any idea's greatly appreciated and I will also try to take the car the next time it snows, or just for a week or so straight to see if I can log this issue happening.
 

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04 Forester XT Manual
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8 Posts
Discussion Starter · #2 ·
So driving to vermont, snowing.... Skipping.... Checked under hood...

How the hell do you stop this from happening? Is this car missing some sort of deflector? I just reinstalled the Part of the air box that the previous owner removed.

Pics of the air filter and in the air box.. The whole underside of the hood had snow by the air box the front of the IC ductwork and over covering the battery, so my issue is obviously snow getting on the maf sensor and causing a spike.
 

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Discussion Starter · #3 ·
Well Ok I'm talking to myself so I'll let you all know what I figure out.
 

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2004 Forester XT Manual
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3 Posts
I've had a similar issue with my 04 FXT... skip feel or slight "bucking" under very light load. Had been doing that since acquisition 6 months ago. Then, it started to get more and more "violent" once in a while, especially when it was raining/snowing. Finally, one day, engine stalled, check engine light came on, two codes (camshaft position sensor malfunction bank 1, missfire cylinder 1). We tested the cam sensor by switching it with bank 2, and code came back for bank 2. Replaced faulty cam sensor, and everything is smooth now, no more bucking or skip feel. Car has 180k km and all sensors are originals.
 

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2012 Forester 4 speed auto
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1,169 Posts
Perhaps, the engine is fine!

A misfire that you describe would most certainly throw a misfire code. Misfires are detected by the cam or crankshaft sensors. When there is a lost of rotational momentum indicated by the flywheel or camshaft the code is thrown. In your situation there isn't a code which tells me the problem isn't the engine. Because the engine was taken out and put back in, I would guess the problem could be the clutch, engine mounts.
 

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Smooshed FOTY 2011
2005 Lifted 2.5 XT 5-Speed MT Dual-Range
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5,732 Posts
If the car feels like it's missing, odds are it's missing. It may not be an actual "misfire", but it's definitely not running smoothly. Check your MAF sensor. Clean it with some MAF sensor spray. I found out that my "missing" was getting worse and worse at time wore on to the point where it started to pull boost and go into failsafe often. I swapped out the MAF with a known good one, car ran perfect. My issue was the MAF.

But the car feeling like it skips or "misses" is a tough one to nail down, good luck.
 

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04 Forester XT Manual
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Discussion Starter · #7 ·
Thank you for some sort of replies... I have some logs from this happening and it's quite possibly not a "miss" that is actually happening, or at least it's not being registered as a miss...

To sum up what I'm seeing in the log is it's a huge MAF spike right when everything happens... this spike follows with Engine Load increasing as well as spark advance dropping and the fueling going really rich.

SO I'm definitely leaning towards this being some sort of moisture or in fact snow getting into the MAF sensor and causing it to read improperly.

I'm also a bit stumped on why this has not thrown a misfire code either since I know on my legacy when I had an issue with water getting on my filter and reaching the MAF sensor that buck threw a random misfire code immediately.

I've thoroughly cleaned the sensor multiple times... and after seeing how much snow was under the hood of this car while driving to VT this weekend there is something I need to address with that.

Anyone have any photos of the front end of the car with the bumper off, or perhaps the proper gaps between the headlight housing and bumper cover? I was wondering if there is any sort of deflector that goes behind that gap as well similar to the seal under the hood because it appears that there is A LOT of snow going between those two items and just blowing all in the engine bay.

A misfire that you describe would most certainly throw a misfire code. Misfires are detected by the cam or crankshaft sensors. When there is a lost of rotational momentum indicated by the flywheel or camshaft the code is thrown. In your situation there isn't a code which tells me the problem isn't the engine. Because the engine was taken out and put back in, I would guess the problem could be the clutch, engine mounts.
I'd almost accept this response but you obviously didn't read the fact that this ONLY happens when it snows... No other times, not even in the rain.
 

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04 Forester XT Manual
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Discussion Starter · #8 ·
here is one of the logs... I stopped them right after it happened so I was able to trim out the beginning of the log to show this...

Maf spikes to 120 g/s and nothing else changes... TP or MAP
 

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Discussion Starter · #10 ·
The first time I will have to take the front end apart will probably be this weekend if that, so I will document as much as I can for bumper gaps and whatnot as well as what I may attempt to do to deflect anything from entering the engine bay and getting sucked up into the intake.
 
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