Inconsistent delays between throttle and rear tire output. Prior Fuel Pump Issues - Pontiac G8 Forum: G8 Forums -
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post #1 of 6 (permalink) Old 06-09-2017, 03:36 PM Thread Starter
Join Date: Jan 2010
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Inconsistent delays between throttle and rear tire output. Prior Fuel Pump Issues

Hello all! I did some searching and some people will probably tell me this is normal, but I'm a little worried because I've already had the fuel pump replaced once on my 2009.5 G8 GT. A tremendously costly fix because of how inaccessible the fuel pump is.

I am starting to see significant delays in power output from throttle to rear tire. It seems very inconsistent and at varying speeds. Yesterday it was as simple as putting the car into gear and going and a few days ago it was when I pulled into another lane and gave her throttle to not cut off an approaching car in the next lane. I quickly went from having enough time to drop the hammer and speed up and away, to being an ******* that switches into a faster lane and goes nowhere.

We're talking about delays up to probably a second and a half. And like I said, varying times and speeds. Car drives fine, and then I experience it.

So the fuel pump was replaced between a year and two years ago. I had similar symptoms before the car finally just started having issues starting.

1. Are people experiencing multiple fuel pump failures in these vehicles? Does this sound like I might be going back down this route?
2. What else should be checked or maintenance done?
3. Would an ECU flash fix these issues? I got contact info for a local guy. I've done flashes on my motorcycles and usually see better throttle response.

Car has less than 70 k on her. She's a joyride car. No commuting, but I sometimes tow a sportbike with her.
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post #2 of 6 (permalink) Old 08-02-2017, 09:53 AM
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subscribed. i have a hesitation. it seems random. i always thought it was the drive by wire and only when heavy throttle activity. helps protect the transmission. i didnt think about fuel pump. it hesitates and then full power comes on. doesn't really happen under light/normal gas pedal use.

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post #3 of 6 (permalink) Old 08-02-2017, 11:20 AM
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Location: North East, MD
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Mechanical fuel pressure gauge, you can get a portable one and tape it up on the windshield if needed, see if the pressure is dropping when it happens.

To rule out the ECM, you're gonna need someone with access to HP Tuners or an equivalent to log what the computer is doing.

Matt Jones
2009 WH G8 GT Vararam/Kooks LT's/Corsa/BLP Probationary LL 219/223 .612/.615 112LSA/3.45s
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post #4 of 6 (permalink) Old 06-29-2019, 09:41 AM
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Any update from this? I've been having similar issues.

HID 6000K--20% all around--tinted tails--tinted sidemarkers--CTS mirror w/custom ambient LEDs--Rotofab--Vleds switchback turns--Corsa CB--Kooks LTs--VMS Tune--H&R Drop

'09 PBM GT
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post #5 of 6 (permalink) Old 07-13-2019, 06:31 PM
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Location: San Antonio, TX
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Mine has been doing it randomly at different speeds. Today I was at around 65 mph and went wot and the hesitation seemed to be the transmission downshift. I have a CAI and definitely heard the throttle open up but it hesitated for about a second when the downshift hit, it then caught the gear and shot forward.

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post #6 of 6 (permalink) Old 07-13-2019, 07:22 PM
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I have experienced this occasionally as well. For me it seems to be from a stop and then moving forward. Could this be what is referred to as pre-detonation? I'm not super technical, so that may be a different symptom. But if so, perhaps it's the fuel being used? I've heard that some gas brands are more prone to this than others.

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