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Discussion Starter #1
Hi,

I have this problem that happen mostly on hot/humid days. At first I thought it was AC related because the compressor strap made some weird noises on startup but I had it checked at the dealer and they say all is good.

The problem is when I need to pass at moderate speed (40+) the power isn't there. I see the throttle at 100%, boost goes as 15-16 PSI and engine revs accordingly, but speed barely changes. As if power didn't go to the wheels (tranny) or boost pressure is lost somewhere between the sensor and the engine. Sometimes it seems tu stutter a bit but performance is not consistent. When the weather is cooler the problem goes away.

There are no codes either for transmission or engine so they told me either you pay for the diagnostic fees or you shut up.

Any ideas, leads or comments on this?

Thanks !
 

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2003 EJ20K Forester
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326 Posts
Time for a new shop if they have that attitude.

The hot/humid day thing suggests that this is a detonation issue. As your intake air temperatures rise, you are more susceptible to knock issues, which would cause the ECM to pull timing, resulting in full boost, and no power. You could take along a code reader and watch your spark advance in real time to diagnose this.

I'm not sure I'm interpreting your post right, are you saying the boost and RPM rise, but not the speedometer? Do you have an automatic or a manual transmission?

What do you call a hot day? Your profile is incomplete, so I have no idea where you live.
 

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Premium Member
'17 Imp Ltd wagon CVT
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1,172 Posts
@Mandor While this thread https://www.subaruforester.org/vbulletin/f107/85-octane-vs-87-octane-800873/ is wide ranging, and possibly partially answers your post, it is not possible to provide further assistance due to your lack of personal information and details. And, you don't even say what vehicle you have. Fill them out.

Posting your details and operational information will show where you were driving as well as the temp, octane used, etc. when the "issue" (which as I see it is owner induced) happened. All are necessary.

I've owned many turbocharged Subarus... all say to use 93 octane, and to expect reduced performance if you don't. Your results will not vary far from that... i.e., using the manufacturer's recommended octane for optimum performance, which is the situation that prompted your post, or be content with the results you're getting, doing what you do.

FWIW, there is no place for the boost to "leak" after the sensor... it IS what is going directly into the engine's cylinders. If you get the boost and get balky performance... it's not your car's fault, at least based on the info so far. Good luck.
 

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2007 Forester Sports XT 4EAT
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@Mandor be advised your thread is subject to being closed if you don't complete your Public Profile.
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