My misfire issues resolved: Faulty blow off valve. (long post, sorry)

The vehicle: 2008 LGT sedan 5EAT, completely stock.

The problem: A serious misfire whenever the throttle was just barely opened. This would occur around 1000 rpms, in park or in gear. Was really noticeable when taking off (slowly) from a stop, or cruising a parking lot looking for a space. My wife would complain of it whenever she drove the car due to different driving habits than mine.

When I pulled codes using my scan tool, I found several misfires logged. I could clear them but they would reoccur, only randomly. P0301, P0302, P0303, P0304. Sometimes individually and sometimes two or more together. I also noted that the exhaust gas temp would rise when the misfiring occurred. I felt like this was probably due to a vacuum leak.

The solution (I hope): I've included pictures that will explain better than I can. I've indicated (on the new valve) the area where my original one separated. I tossed my old one before it occurred to me to post this. Basically, my blow off valve (BOV, by-pass valve, pressure relief valve, or whatever else you want to call it) had come unglued The top or "cap" had begun to separate for the base. Apparently these things are glued together. This is the area where the diaphragm is housed. When idling (full vacuum), there was no leak, but under partial throttle the diaphragm would drop and a leak would be created. I replaced the valve yesterday and so far, so good. Runs better overall, but especially when driving like a granny. My wife will be pleased

Good logic! Glad to see it is fixed.

Thanks.

The bad part about this is when I checked with my dealership to see if the valve would be covered even though I was about 2500 miles out of warranty.

One of the mechanics raised the hood, acknowledged that, yes, my BOV was cracked, then proceeded to tell me that that would have nothing to do with causing a misfire. He asked if I was running genuine Subaru plugs to which I replied yes (I really am).

Then he dropped the bomb: He stated that if my engine was misfiring then I had cracked ringlands. Period. No discussion about injectors, coil packs or any other specifics. And remember, my car's bone stock.

When I questioned how a leaking BOV could not be causing a problem, he said I could replace it if I wanted but it wouldn't be under warranty and "he was just trying to save me some money". He then went on to say he would be glad to do a compression check and, if need be, replace any affected pistons. I bet. I knew this was a sorry excuse for a dealership, but I was amazed at this.

I just went ahead and ordered the valve (since it was bad anyway). I'm glad I did.

Wow good catch. I'll have to keep an eye on mine now.

Oh yeah, tell the dealership to pound sand.

Thanks.

... when I checked with my dealership, one of the mechanics proceeded to tell me that my engine was misfiring because I had cracked ringlands.

What a moron!

I noticed that there are certain parts of the country where Subaru dealer service obviously suffers. You must live in one of those areas.

Yeah, East Tennessee (Knoxville area). I'm 43 (old in other words) and there's not been a good Subie dealer here in all the years I've been driving. I've always just done my own service 'cause I decided I like the product years ago. The bad part is I've known people over the years in this area who've had Subarus and think they're junk because of crap like this.

Yeah, East Tennessee (Knoxville area).

The bad part is I've known people over the years in this area who've had Subarus and think they're junk because of crap like this.

That is unfortunate. Here in the Milwaukee, Wi area we have several dealers which are as good as other Japanese brands. One dealer however has standards that are above and beyond all the others and makes you feel as though you are driving a luxury brand. When I lived in Seattle the Subaru dealers there had good reputations. (I was not driving a Subaru then, but nobody I knew ever bad mouthed the brand)

I have seen several dealer horror story posts here from members in the New York & New Jersey area. I think that might be the worst.

Oh Texas seems to be bad also.

(Sorry for the thread jack, but it seemed relevant when i started posting)

The vehicle: 2008 LGT sedan 5EAT, completely stock.

 

The problem: A serious misfire whenever the throttle was just barely opened. This would occur around 1000 rpms, in park or in gear. Was really noticeable when taking off (slowly) from a stop, or cruising a parking lot looking for a space. My wife would complain of it whenever she drove the car due to different driving habits than mine.

When I pulled codes using my scan tool, I found several misfires logged. I could clear them but they would reoccur, only randomly. P0301, P0302, P0303, P0304. Sometimes individually and sometimes two or more together. I also noted that the exhaust gas temp would rise when the misfiring occurred. I felt like this was probably due to a vacuum leak.

 

The solution (I hope): I've included pictures that will explain better than I can. I've indicated (on the new valve) the area where my original one separated. I tossed my old one before it occurred to me to post this. Basically, my blow off valve (BOV, by-pass valve, pressure relief valve, or whatever else you want to call it) had come unglued The top or "cap" had begun to separate for the base. Apparently these things are glued together. This is the area where the diaphragm is housed. When idling (full vacuum), there was no leak, but under partial throttle the diaphragm would drop and a leak would be created. I replaced the valve yesterday and so far, so good. Runs better overall, but especially when driving like a granny. My wife will be pleased

Sounds like the issue I'm having. You can definitely feel the misfire. I'll check out the BOV.