Thread: 2008 Grand Prix losing power going up hill

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  1. #1 2008 Grand Prix losing power going up hill 
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    My Grand Prix started losing power when going up hill just started today.Check engine light flashes when it happens then stops when car hits level ground no fault codes showing thanks for any help
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  2. #2 Re: 2008 Grand Prix losing power going up hill 
    GTX Level Member cheatah faheatah's Avatar
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    No codes ? Says what ? DIC? or actual scan tool ?
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  3. #3 Re: 2008 Grand Prix losing power going up hill 
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    scan tool
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  4. #4 Re: 2008 Grand Prix losing power going up hill 
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    K, swierd. I thot 4 sure a flashing cel would set a code ?
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  5. #5 Re: 2008 Grand Prix losing power going up hill 
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    Does it also flash during WOT?
    Pre-Production 2004 GP GTP Comp G / 91,000mi / TransGo Shift Kit, Spectre Open Cone, 180 Tstat, AL605's, ZZP 3" catted DP, ZZP front PLog, Intense PCM, GMPP Sway Bar
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  6. #6 Re: 2008 Grand Prix losing power going up hill 
    Killa Bee Scottydoggs's Avatar
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    clogged cat or it needs a tune up super bad.

    scan the car running after it flashes, it might show a pending code. pending codes can clear if you shut the car off.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  7. #7 Re: 2008 Grand Prix losing power going up hill 
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    Quote Originally Posted by Scottydoggs View Post
    pending codes can clear if you shut the car off.
    Ahhh..
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  8. #8 Re: 2008 Grand Prix losing power going up hill 
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    Scotty just started getting a po300 code new plugs and wires last year
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  9. #9 Re: 2008 Grand Prix losing power going up hill 
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    Did not try this
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  10. #10 Re: 2008 Grand Prix losing power going up hill 
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    Showing a p0300 code after a rescan
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  11. #11 Re: 2008 Grand Prix losing power going up hill 
    Killa Bee Scottydoggs's Avatar
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    how many miles it got? ever been tuned up ? 300 is the multiple misfire code.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  12. #12 Re: 2008 Grand Prix losing power going up hill 
    Killa Bee Scottydoggs's Avatar
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    Quote Originally Posted by daviddawg View Post
    Scotty just started getting a po300 code new plugs and wires last year
    missed this post, miles? cat might be clogged.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  13. #13 Re: 2008 Grand Prix losing power going up hill 
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    Got 120000 on car new plugs and wires at 100000 also had to change ignition control module at same time and a bad coil . Just found out when in park and rev up engine noticed it wont rev past 3500 rpms
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  14. #14 Re: 2008 Grand Prix losing power going up hill 
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    No flash but will only rev up to3500rpm
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  15. #15 Re: 2008 Grand Prix losing power going up hill 
    I live here. stealthee's Avatar
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    That's how it is supposed to be. That is a safety feature.

    Also there is no flash because there is no load. If you want to put load on the engine put it in drive and with your left foot on the brake hit the gas with your right.


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  16. #16 Re: 2008 Grand Prix losing power going up hill 
    GT Level Member Gregorius's Avatar
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    Here's a funny thought.

    What if was a clogged fuel filter, and the fuel pump had enough on level ground, but once it had to pump "uphill" too......lol would also explain the P300's.

    I'm still drinking coffee, ignore me.
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  17. #17 Re: 2008 Grand Prix losing power going up hill 
    Killa Bee Scottydoggs's Avatar
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    not, heres the deal, flashing cel means one of two things almost always. cat, or needs a tune up real bad.

    pull the o2 sensor to make a exhaust leak pre cat, it should run better if the cats bad, sound like crap tho.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  18. #18 Re: 2008 Grand Prix losing power going up hill 
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    A flashing CEL means its breaking NOW. Attaching a scan tool and reading whats going on. Looking at long term and short term fuel, o2 readings, misfire counters if available.
    One old time test for fouled cat is warm engine then rev it up and hold it at around 2000-3000 rpm and I like sitting a plastic jug about for or so away from exhaust pipe. Generally if converter is plugged the exhaust is forced through smaller area and super heats converter and exhaust and can be felt at tail pipe.
    Proper diagnosis starts with reading PIDS. Fuel psi , air in, LT/ST, map, IAC if equipped, o2 ranging, misfire counters per cylinders.
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  19. #19 Re: 2008 Grand Prix losing power going up hill 
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    Thanks for everyones input.Up date on problem found an vacuum hose leaking replaced hose car ran better but still starts losing power when you get up to 40 miles an hr.
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  20. #20 Re: 2008 Grand Prix losing power going up hill 
    Killa Bee Scottydoggs's Avatar
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    cause clogged cat.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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