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Hondafan 01-01-2011 01:20 PM

08 STi not boosting.
Starting yesterday, I am not boosting over 10 PSI. The car is stage 2 with a catted Cobb DP, Blitz CBE, and an AP with an OTS map from Cobb. The car was boosting 17-18 PSI I believe, but now it's usually boosting about 8 PSI and I was able to get it to 10 PSI in fourth going up a canyon freeway. AFR is remaining at around 11 under WOT conditions, the car shows no ignition advance/retard. I parked it outside overnight, which I don't normally do, but I've been working on my dad's car in my garage so I left my car in the cold. I've warmed up the car and drove it for a couple hours total yesterday as I took it snowboarding. WG Duty is not doing anything at all. I don't know that it would do anything below target boost anyway. I can't find any vacuum leaks, and I also have no exhaust leaks either. It also does some weird surging (under minimal boost) while I leave the throttle in the same position. It's worst right when the turbo should be spooling up around 3K-3.5K. The surging feels most like a spark-based lag, but the car only has 18K on it, so I can't imagine there'd be an ignition problem. . . I could be wrong? This was rather sudden, and I only noticed it yesterday morning, but I had done a bit of freeway driving the night before so I hadn't really pressed the throttle, but it definitely started within the last 48 hours.
I have an appointment on Monday at 7 AM at the dealership for them to take a look at it, but if it's something I can do, I prefer to fix stuff myself.

basco 01-01-2011 04:09 PM

Do a boost leak test

newtothegame 01-01-2011 09:48 PM

Im with Matt, try to look for boosts leaks. But if you do think its a spark issue, might need to make room in the garage and pull the plugs to give them a once over. Good luck with finding the problem and getting it up an running strong again.

Hondafan 01-01-2011 11:08 PM

Here's another twist to throw in:

I got in the car this morning and the car cranked REALLY slowly, and didn't start for probably about 10 seconds, then it drove like it had a misfire for a little bit, but once I got on the freeway it actually pulled hard again, and it was boosting normally. THEN on my way home today, it was doing the weird surging thing again and it wasn't reaching full boost. I'll search for the way to do a boost leak test and try that, but would it really be intermittent? I was okay about taking it to the dealer when it was constant like it was for the whole day on New Year's Eve, but Techs never see the intermittent issues, because they never happen when the guys are trying to make it happen. It's also getting TERRIBLE fuel economy, like 17 on the freeway. Is it possible that it's gasoline that's still working out of the tank? It's been really cold here but I hope that's not really a factor.

man show 01-03-2011 08:21 PM

Yeah, my car has been acting very similar to what you've described lately too. I can't quite figure it out. I thought it was the wind hitting my roof rack and fairing and making the car feel like it's surging under boost, but it happened in all gears and in varying situations. It's not the first time it happened, but it hasn't done it in quite a while. I'm considering switching gas temporarily from Shell 93 to something else because I'm thinking maybe the winter blend is the culprit. That, or possibly running a bottle of fuel injector cleaner through it on my next fill up. Each time it happened, I had been driving on the highway for a little while and I believe both times I was going up hill with the engine under a moderate amount of load, but it didn't stop when the load was removed. It's almost as if the ecu was trying to correct something that wasn't really wrong. After turning the car off and letting it sit over night, the problem went away both times. Really interesting. My gas mileage is also horrible right now (I'd be lucky to get 300 miles out of a full tank), but I drive a lot on the highway and I'm pretty sure it's due to wind resitance from the roof rack. The first time, I plugged in my AP and tried to monitor all the parameters, but everything looked pretty normal to me. Then I thought maybe my turbo was on its way out, but the problem went away both times after doing nothing but shutting the car off and letting it sit for a while. Let me know if you figure anything out with yours.

Hondafan 01-04-2011 12:37 AM

The dealership found that it was misfiring on 3 of the 4 cylinders, and mostly on #4. I don't understand the entire readout they gave me, but they diagnosed it as a bad tank of fuel, and then the ECU threw itself into some weird fail safe mode that wouldn't allow it to boost over 10-ish lbs. They reset the ECU, and then they said it shouldn't be boosting at 17.8 psi and that any other issues it would have were due to the DP. They're not super mod-unfriendly at my dealer, and I understand they can't diagnose an overboost type situation with the DP installed, but since then, the car has been running fine. I uninstalled the AP just to see if it would pull a code or anything and start acting up again. After I've run through this tank I think I'll be satisfied that it really was fuel. They also thought if it wasn't gas then it was a faulty map that was loaded (even though I haven't changed it in 3 months). If it acts up again I'll find a stock DP to install and take it back in to them, as they don't mind that it was done already, just that they won't diagnose it further until they can rule out modification factors. Hopefully that's all I need to worry about and I don't actually have to go through the work of swapping it.

pzr2874 01-04-2011 05:33 AM

Any firmware updates ?

Hondafan 01-04-2011 02:33 PM

I updated the firmware in August or September, because the AP was originally for my WRX. I called Cobb and they told me all I had to do was update the firmware for an STi and that it would work. It did. I haven't honestly touched the map since I changed it in August. There have been no changes to the car performance-mod-wise since then. I haven't tried updating the firmware since then though. I've been trying to decide whether to buy sways and links or an equal length header, in which case I'd have Perrin make the custom map like they did when I got my stage 2 setup from them, so I've been content with the OTS AP map for now, as I think my last power mod will be the ELH. I've got to ask RcrsWetDream who his tuner was again here in SLC, and maybe I'll go that route after the header.

RcrsWetDream 01-04-2011 05:30 PM

1 Attachment(s)
^Jason Cleverley aka medamullet on Slcsubaru. He's never on there though, he's on Nasioc a lot under the same name.

pzr2874 01-05-2011 06:02 AM

Whats with everyone and manifolds... Get the stocker PnPnC.... Save yourself some headaches.

Just sayin.

RcrsWetDream 01-05-2011 07:53 AM

1 Attachment(s)
PnP FTW.... Great for a smallerish turbo setup. Headers do seem to outperform once you go big though.

man show 01-05-2011 10:03 AM

Interesting, thanks for the update. I don't imagine my issues would have been caused by anything other than gas. I didn't make any other changes before or after the hesitation started and stopped. My car must have magicical powers because it fixed itself.

Hondafan 01-06-2011 03:37 AM

Here's the verbatim report from the Subaru technician:
Test drive to verify concern, max boost seen was 10.8 PSI. A/F corrections were maxed out on both ends of the spectrum at +/- 25%. Misfires were found multiple times on cylinder four. Cleared system memory and drove again. Max boost seen was 17.8 PSI (Note the vehicle was not in Sport Sharp Mode, indicating a tune has been installed on the vehicle), A/F Corrections were still maxing out and misfires were now present on cylinders 1,2, and 4, multiple times on each. Signs point towards either bad fuel (contamination or improper octane rating), or a faulty tune. Advised customer to try a fuel system cleaner and running at least 2 tanks of premium fuel. If the concern does not change, it will be necessary to remove the tune and all aftermarket "Power Adders" and attempt to diagnose vehicle under stock conditions.

My biggest concern is that the problem has returned now, although it's not quite as severe. I keep forgetting to run fuel cleaner, but I've never run anything other than premium, so I'm doing half of what they wanted. I found a downpipe locally to revert it to factory. That sucked to pay $225 from a junk yard to get a part just for diagnosis' sake. I wanted to have the factory parts anyway still, so not really a loss. I'm swapping the downpipe/midpipe tomorrow morning and then setting up the appt for Subaru to take a look at it again. I think it's weird that I've not gotten a CEL from this still. Other cars I've owned pull a code for a misfire before I even feel it in the acceleration. Oh well, hopefully the professional attitude I am giving to Mark Miller Subaru continues to pay off and they don't try to find a reason that the DP could have caused this. . . I really want to know what it is more than anything. Unless all of the gasoline in the valley here is all crap. I think we'd see more people complaining if that were the case though.

Thanks, Chris for Jason's info! I want to go see him when I get the header installed.

RcrsWetDream 01-06-2011 08:47 AM

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[quote=Hondafan;255026]Thanks, Chris for Jason's info! I want to go see him when I get the header installed.[/quote]

NP, if you need his phone number just shoot me a PM. He's on my speed dialROFL I buy all my stuff through him too, he has a company so he gets me stuff pretty much at cost!Thumbs Up

Oh and I think he charges $250 for road tunes now.

pzr2874 01-06-2011 09:06 AM

"Power adders".... I hate Subaru/SOA for this exact mentality.

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