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post #1 of 4 (permalink) Old 01-17-2008, 08:55 AM Thread Starter
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Electronic throttle control problem

Well...I attempted to post this problem under General Discussion, with no success...Let' s try here in Tech. My friend just installed a 454 LS7 based stroker small block in his 2004 GTO. The rear wheel dyno indicates 562 peak rear wheel H.P. and over 500 ft/lbs torque thru a broad range of RPM. His car is an auto tranny car with 3600 RPM stall converter.

Here' s the problem....These cars have an electronic signal from the accelerator pedal which controls throttle position( I am old school and am familiar with mechanical linkages ) so this is new to me. With this motor, there is a 'Dead Zone' which lasts about 0.4 seconds from the time you mash the throttle pedal to the floor until the signal is recognized at the plenum. This is not a stumble or any type of engine hesitation. I just don't think the signal is being transmitted immediately. If you load the converter and power brake, this problem is non-existent.

Does the computer have some type of safeguard which can be bypassed to allow immediate WOT under any and all driving conditions or is there some other explanation for this delay. Thanks for any and all assistance. David
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post #2 of 4 (permalink) Old 01-18-2008, 07:20 AM
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Sounds like a bad ass engine install!
Do you guys have a scan tool to read what the switch is doing? If so, is the delay showing on the scan tool too?
I`m not sure how they are set up, but is there a MAF sensor between the air cleaner and the throttle body? If so, is that hose leaking or collapsing at all when you accelerate hard?
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post #3 of 4 (permalink) Old 01-18-2008, 07:32 AM
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I believe the 2004 GTO used a cable rather than the fly by wire set up offered on the 2005 LS2 GTO. Did your friend change the PCM and throttle position sensor to the setup used on the LS2/LS7.

Another option would be to change the throttle body to a LS7 90 mm cable operated TB.


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post #4 of 4 (permalink) Old 01-18-2008, 10:25 AM Thread Starter
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05GTO and Rukee,

Thanks for your input. There are no leaks around throttle body and all the necessary LS1 to LS7 conversions, including TPS have been done. Many hours with laptop and rear wheel dyno already logged. It seems that, besides the delay, below 1500 RPMs, the computer is taking all the timing advance out? The car screams if the converter is loaded (actually it just relentlessly smokes the tires), but from a dead tromp, it's almost acting like you are running a delay box. Maybe the 90MM LS7 cable operated throttle body set up would be the way to go...I am old school... and I say YES... Unfortunately, the owner is a techy and he will want to struggle to unravel this mystery electronically. Again, thanks for the input. David
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