NO power at high altitudes
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This is a discussion on NO power at high altitudes within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I drove my 04 wrx to South Lake Tahoe for the first time since I bought my car a few ...

  1. #1
    Registered User taz77's Avatar
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    NO power at high altitudes

    I drove my 04 wrx to South Lake Tahoe for the first time since I bought my car a few weeks ago. I'm in San Francisco at sea level, the area of Tahoe I was at was about 5000+ feet above sea level. As soon as I get to Tahoe, I notice a serious lack of power when I'm accelerating from a stop. I understand that due to the thinner air at higher altitudes, performance will decrease to a certain extent... BUT my 4 year old nephew will out run me across an intersection (not that I tried... but he could have) ! It can take about 4 seconds just to make it halfway through the intersection. Once I build up speed, It'll be ok, but there is a SERIOUS lack of acceleration from a stop.

    First, I thought maybe my wastegate might be stuck open or something from running 3000rpm for 2 hours, but when I drove home and got back down to Placerville, my car accelerated near normal speeds... and back in the nice, cold, dense foggy air of San Francisco, boy does it accelerate.

    I'm no expert in Subarus, or in turbos for that matter, but I thought the ecu would use either the MAP sensor, or a baro sensor if it's equipt with one to read atmospheric pressure and compensate.

    I'm hoping someone can shed some light here on what might be going on. I haven't found anyone else with the same problem online... and I couldn't find any TSBs in this matter. For reference, I'm running stock everything except for a SPT intake and exhaust.

    Any info that can help out here is much appreciated!

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  3. #2
    Registered User 68sprintb's Avatar
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    subaru does run a MAP sensor & MAF, odd it wasnt updating the baro as you drove though... did you ever got WOT (~80%) at a low (~2000) RPM? that is typically when it updates...
    Blobeye Syndicate #75
    2005 OBP WRX Sport Wagon
    Stewart Warner Boost & Oil temp gauges / OEM 20 mm rear bar
    Cobb stg 2 / STi uppipe / Crucial Racing downpipe
    Stromung 2.5" catless centerpipe / Scooby Sport New Age centre pipe & backbox

  4. #3
    Registered User taz77's Avatar
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    I did go WOT the first time I noticed the problem trying to cross traffic, and rpm at the time was probably just off idle... 1k rpm maybe. However, it was only a brief period of maybe 3-4 seconds. Once I noticed there was an issue, I let off the throttle. I also tried the update by holding the throttle WOT at key on engine off for 5 seconds. Needless to say, that didn't work.

    The only thing I can add to is that temperature is not the cause. It's the same in the morning at 50 degrees, as it is late afternoon at 80%

  5. #4
    Registered User 68sprintb's Avatar
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    yeah holding the throttle at WOT at KOEO isn't necessary as it should update at initial key-up while there isn't no vac or boost... it'd be nice if subaru provided a better data stream, instead they put all the good stuff on the proprietary DLC... weird though...
    Blobeye Syndicate #75
    2005 OBP WRX Sport Wagon
    Stewart Warner Boost & Oil temp gauges / OEM 20 mm rear bar
    Cobb stg 2 / STi uppipe / Crucial Racing downpipe
    Stromung 2.5" catless centerpipe / Scooby Sport New Age centre pipe & backbox

  6. #5
    Registered User taz77's Avatar
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    Any idea how long it takes to update? I just noticed that if I'm at a stop, and go WOT, I can only keep it below 2000 rpms for no more than 2 seconds.
    Timothy Lee
    Toyota Certified Expert Technician
    ASE Certified Master Automotive Technician
    ASE Certified Advanced Level Engine Performance Specialist

  7. #6
    Registered User 68sprintb's Avatar
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    as long as it take the PCM to see high throttle at low RPM, so about 30 micro-seconds
    Blobeye Syndicate #75
    2005 OBP WRX Sport Wagon
    Stewart Warner Boost & Oil temp gauges / OEM 20 mm rear bar
    Cobb stg 2 / STi uppipe / Crucial Racing downpipe
    Stromung 2.5" catless centerpipe / Scooby Sport New Age centre pipe & backbox

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