My STI has been having a very odd lean spot/buck ever since I installed injectors and a walbro. I was hoping someone here could provide some alternative insight as what is going on, and what the culprit could be.
Car:
08 STI
DW 850cc's
Walbro Pump
Cobb AP, protuned
AEM CAI
P&L TBE(catless)
Perrin BOV
Symptons:
Ranging from 2500 to 3000 rpm(and usually stopping at exactly 3k) when cruising on the hwy usually in 5th and 6th and applying a light load, the engine will begin to buck/stumble. Its very odd and when looking at my data logs the one that stands out is the AFR. As soon as the bucking hesitation starts, the AFR's jump from 14 to 15 to 16 and sometimes 17. Once I hit 3k rpm afr's would go back to normal and the car would seem fine.
Another way I can tell is in start stop traffic, the car really doesnt like being shift below 3k rpm, and if I rev match to a lower gear, u can feel it stumble a bit if its below 3k.
Attempts to fix:
When the symptom first came about, Stephen at IAperformance and I spent countless hours etuning the car with no real result. After contacting other tuners, Stephen recommended I revert the current FPR system on my car to that of an 07 STI. We tried this and not much had happened. Finally, my housemate who is the local OS tuner decided to give it a whirl w/ AccessTuner Race. I figured this may net a better result since this time the tuner will actually be in the car and it could be easier to diagnose. We spent some time road tuning using the cobb stg 2 v104 maps as a base and voila it was gone.
Fast forward to now, roughly 3 months later, I'm driving home from getting the car serviced and the stumble/hesitation is back. The car was just getting an oil change and a tech inspection, I was there the whole time w/ the mechanic as well, so I know nothing other than an oil change and tech inspection occured.
When I got home I cleaned the MAF, changed the spark plugs(was going to do it that day anyway), reset the ecu, and ran an older map. Stumble was still there. So I reset the ecu again and ran the most current map, for a while it seemed as if the stumble had disappeared, but then it came back about an hour later.
The only thing I can think of that changed in the last 3 months is the weather. I live in Pensacola and the summer weather has finally arrived with temps in the upper 80s to mid 90s.
Like I said earlier, if anyone has any ideas as to what is causing this problem and has a possible solution please post up. While researching I read that it could also be a clogged PCV valve(I'm going to pick one up tomorrow and install it this weekend).
Car:
08 STI
DW 850cc's
Walbro Pump
Cobb AP, protuned
AEM CAI
P&L TBE(catless)
Perrin BOV
Symptons:
Ranging from 2500 to 3000 rpm(and usually stopping at exactly 3k) when cruising on the hwy usually in 5th and 6th and applying a light load, the engine will begin to buck/stumble. Its very odd and when looking at my data logs the one that stands out is the AFR. As soon as the bucking hesitation starts, the AFR's jump from 14 to 15 to 16 and sometimes 17. Once I hit 3k rpm afr's would go back to normal and the car would seem fine.
Another way I can tell is in start stop traffic, the car really doesnt like being shift below 3k rpm, and if I rev match to a lower gear, u can feel it stumble a bit if its below 3k.
Attempts to fix:
When the symptom first came about, Stephen at IAperformance and I spent countless hours etuning the car with no real result. After contacting other tuners, Stephen recommended I revert the current FPR system on my car to that of an 07 STI. We tried this and not much had happened. Finally, my housemate who is the local OS tuner decided to give it a whirl w/ AccessTuner Race. I figured this may net a better result since this time the tuner will actually be in the car and it could be easier to diagnose. We spent some time road tuning using the cobb stg 2 v104 maps as a base and voila it was gone.
Fast forward to now, roughly 3 months later, I'm driving home from getting the car serviced and the stumble/hesitation is back. The car was just getting an oil change and a tech inspection, I was there the whole time w/ the mechanic as well, so I know nothing other than an oil change and tech inspection occured.
When I got home I cleaned the MAF, changed the spark plugs(was going to do it that day anyway), reset the ecu, and ran an older map. Stumble was still there. So I reset the ecu again and ran the most current map, for a while it seemed as if the stumble had disappeared, but then it came back about an hour later.
The only thing I can think of that changed in the last 3 months is the weather. I live in Pensacola and the summer weather has finally arrived with temps in the upper 80s to mid 90s.
Like I said earlier, if anyone has any ideas as to what is causing this problem and has a possible solution please post up. While researching I read that it could also be a clogged PCV valve(I'm going to pick one up tomorrow and install it this weekend).
) your fault, not the tune or the car, and is only that one hiccup that is quickly learned away. 
