low boost issue

Discussion in '2007+ Mustang GT500 Tech' started by Mad, May 28, 2016.

  1. Mad

    Mad Moe

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    hi all

    i have a 2010 GT500 with few mods running 13-14 psi on the supercharger. last night I have noticed power loss, after checking I realized that am loosing boost. my super charger does 4-6 psi now ! I have looked for any fault codes but found none. and my water pump is running perfectly.

    please help
     
  2. Wes06

    Wes06 forum member

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    check any hoses on the manifold check if lines are cracked and bleeding off?
     
  3. Marble

    Marble forum member

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    I would guess an issue with the bypass valve.

    A vacuum gun that can pull fashion and create pressure will let you know if you have a leak.

    Is the belt slipping?

    All sorts of possibilities...
     
  4. Mad

    Mad Moe

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    Thanks for the input guys

    Belt is not slipping
    I will check the other possibilities today

    Is tunning a possibility?
     
  5. Wes06

    Wes06 forum member

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    I can't imagine tuning is reducing boost
    Unless the cam angles are so far off its letting all the boost bleed by with both valves open at once.

    Can the gt500 cams be independently restarted?
    Or is that just the coyote
     
    Last edited: May 29, 2016
  6. redfirepearlgt

    redfirepearlgt forum member

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    Would doubt belt slippage would effect boost by 10psi on a 13-14 psi setup unless the belt is on its very last leg. Your water pump moving coolant well enough is a pretty clear indicator of that(assuming its belt driven). I would suspect other issues is the belt was so bad that you were losign 10psi of boost due to a failing belt...but wierder things have happened.

    BP valve or better yet bypass valve vacuum actuator hopefully as it was for me. With car off bypass valve will release. Started and running it will be in bypass due to vacuum state at idle. If it is mechanically stuck as mine was you will see little to no boost on your vacuum boost gauge when you mash the go pedal.

    Start the car and allow it to build vacuum at idle. Find the bypass valve and observe the position. With car running pull the vacuum hose on the bypass valve and observe if the actuator rod changes position. If it does make sure it completed it's stroke and did not hang up part way. Hanging up or not moving is bad. Plug the vacuum line and pop the throttle and see if boost is now present. If it is with the vacuum hose disconnected from the bypass actuator, then you have isolated the problem. Now its simply a matter of determining if its internal or simply the actuator.

    The PCM/tune will not effect boost output on a TVS, however vacuum may vary depending on cams and tune at idle to some degree. Loss of boost is mechanical. its simply a matter of isolating it. Good luck. BTW vacuum actuators are reasonable and you can replace that yourself.
     
    Last edited: May 29, 2016
  7. Mad

    Mad Moe

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    Thanks for all the input guys, this is really helpful
    I just took my car to a workshop will see how does it go
     
  8. redfirepearlgt

    redfirepearlgt forum member

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    Any update? Just curious.
     
  9. 01yellerCobra

    01yellerCobra forum member

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    That's just the Coyotes. The GT500's are old school in that regard.

    The water pump should be on a different belt from the blower. So the water pump turning fine won't affect the blower. Usually a belt giving up leaves evidence. Lots of black dust, squealing, etc. I'd go with the BPV as well.
     
  10. Mad

    Mad Moe

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    Am still waiting for the mechanic to call me....
     
  11. Mad

    Mad Moe

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    Whats a bpv ?
     
  12. Wes06

    Wes06 forum member

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    Bypass valve
    The part that closes at WOT and let's boost build
     
  13. redfirepearlgt

    redfirepearlgt forum member

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    so what was the outcome? Inquiring minds want to know...
     
  14. redfirepearlgt

    redfirepearlgt forum member

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    nothing but crickets...
     
  15. Mad

    Mad Moe

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    Hey guys
    So my mechanic tells me the car
    Is low on compression and the variation in compression numbers between cylinders are very big like 60 to 70 degrees difference

    I dont really fully understand but he says i need an engine rebuild
     
  16. Mad

    Mad Moe

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    Please read above
     
  17. redfirepearlgt

    redfirepearlgt forum member

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    Just FYI - Compression is measured in two ways. There is an actual compression gauge that is used to check each cylinder while cranking the engine over with no spark. Then there is a leak down test which measure pressure loss in each cylinder over time. Either way it is a measurement of pressure based on piston cylinder compression with regard to integrity of the cylinders ability to remain sealed on the compression stroke. This failure could be due to various valve issues, piston ring issues, cracked piston issues, warped/lifted heads, or head gasket issues. Further a poor compression or improperly performed compression check can also produce erratic information. I suggest posting the specific data he provided you OR better yet contact Ford technical support and provide them with the data he is giving you.

    The basic things that would come to my mind with regard to symptoms of this nature are...Does the car burn oil? Is there a smell of fuel or oil in the coolant? Is there coolant loss with a presence of coolant vapor coming out the exhaust (not to be mistaken for start up condensate)? Does the car produce heavy amounts of exhaust smoke at hard throttle or at sudden throttle up or deceleration? And of course severe power loss? Obviously you are experiencing the latter and this could still be a bypass valve issue. But with compression tests varying as much as he claims (assuming degrees really means PSI) there should be other tell tails as well such as described.

    Good luck. Poor compression COULD be a culprit but personally I would get a second opinion before saying okay to a $7000+ engine rebuild. I've been there. Took the advise of a shifty Ford service tech center who claimed I had failing valve guides in a 2002. Replacing the heads resolved nothing to keep the story short. The end was justified when they were forced to close by Ford some months later. I later ran into one of the service writers at another dealer and he remembered me and told what REALLY happened, but that is neither here nor there. Simply to point out getting a second opinion. Again best of luck and thanks for the update. Let us know what pans out.
     
    Last edited: Jun 13, 2016
  18. 01yellerCobra

    01yellerCobra forum member

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    I had a D1 on the stock engine in my 01 Cobra. I knew I had two bad cylinders. When I removed the heads I found out I had three broken pistons. That engine still made 12-14psi with broken pistons. I know it's not the same set up, but food for thought.

    If you don't understand what he said scan the paper work and post it here. We don't want you getting taken for a ride.
     
  19. Mad

    Mad Moe

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    Am trying to get a bypass valve/actuator whoch seems to be the problem but its nowhere to be found
    Does anyone know where i can buy it from ? The stupid dealer have no idea
     
  20. Speedboosted

    Speedboosted Found missing cylinders

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    Tasca Parts or any major shop might have a few extra laying around. Revan, BPS, JPC, VMP, Power By the Hour, Weir Racing.