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post #1 of 18 (permalink) Old 02-21-2015, 01:01 AM Thread Starter
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Any ideas?

Hey guys, so today I was washing my grandmas car and I had my G8 in the carport to avoid getting wet. I haven't had any issues major yet in the 35k I've put this last year except replacing the fuel pump at 88k, and a new alternator somewhere in the mid 60's. Well I went to start my car with the remote start after it sitting for about an hour and a half and instead of the usual full loud initial exhaust note, it sounded rather weak and didn't have much behind it. I went inside to start the car and it did the same thing, it had a weak initial start up exhaust note, and I noticed the voltages dip down to 10-11 but almost immediately went back up to 14.

About 3 hours later. I had my car sitting for about 2 hours this time, go inside to start it up so I can go to work. It again start up fine, but just sounds and feel weak and sort of had a chugging feeling/sound but only for about 5 seconds or so then pepped up just fine. It drives and sounds fine and the voltages are fine while the car is idling/driving. It starts up just fine to if I had the car running recently or if I turn it off and on.

Any ideas?

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #2 of 18 (permalink) Old 02-21-2015, 10:13 AM
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Does the starter turn over more slowly? If your battery is weak or low on charge, the alternator will dump current as directed by the voltage regulator into recharging, along with running the electrical system. Are you now in the cold below freezing when the car is normally in a mild climate? This will leave your battery taking more time to accept a charge, especially if you take short drives. It's easy for a battery to hold charge for a whole and a warm start does not load it as much obviously. It seems like you may have a temporary shorted cell in the battery if it is gobbling enough current from the alternator to drop voltage down to 10. ..as if the plates may be heating up with the charge from the alternator, then clearing the short. The voltage should hold around 14 no matter what RPM but if you see it rise to 15-16 on higher RPM and drop to 11-12 at idle, that points to the alternator losing one phase in the rectifier pack. Get that battery checked out.

[SIGPIC][/SIGPIC]09.1 G8 GT Sp. Prem. w GXP Facia. Roto Fab covers +chrome caps / Spyder Tail Lamps/VIM Hack c/w rear cam. BMR Sways/ Arms/ Toe Rods/ Rear Cradle Inserts+ Diff bushings/H&R Coilovers / Russell ss lines w CTSV Calipers+2015 SS Rotors . Staggered Avant Garde M310's . KOOKS Mids w HFCs. Corsa w Volant CAI /Dr. Phil 91 Octane Tune on Dyno. RCR Intake & TB/Catch Can w Little Lunati DoD Delete. ZL1 Converter and CNC'd heads by Aggressive Performance MI.
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post #3 of 18 (permalink) Old 02-21-2015, 10:18 AM Thread Starter
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Check engine light came on this morning. I dropped it off at the mechanic 15min ago. I'm in San Diego. It rarley dips below 50 here, and I keep the G in underground garage parking. The car turns over just fine. Its right after where it sounds and feels off
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post #4 of 18 (permalink) Old 02-21-2015, 02:03 PM Thread Starter
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Got it back. They said it was throwing 2 codes. Can't remember off the top of my head what they were but he said it was misfiring during cold start up. He said some gunk might have gotten in my fuel system so he put some cleaner in. Told me if the engine light comes on again I'll need to change my plugs

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #5 of 18 (permalink) Old 02-21-2015, 03:05 PM
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Quote:
Originally Posted by SDpiel8 View Post
Got it back. They said it was throwing 2 codes. Can't remember off the top of my head what they were but he said it was misfiring during cold start up. He said some gunk might have gotten in my fuel system so he put some cleaner in. Told me if the engine light comes on again I'll need to change my plugs
That was weird how the voltage was collapsing... maybe not if you were running at 350 RPM at which point the alternator would not produce enough voltage. Any lower than that and you would stall. If you have not ever changed the plugs just go ahead and get that done.
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post #6 of 18 (permalink) Old 02-22-2015, 08:25 AM Thread Starter
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Quote:
Originally Posted by FMQ View Post
That was weird how the voltage was collapsing... maybe not if you were running at 350 RPM at which point the alternator would not produce enough voltage. Any lower than that and you would stall. If you have not ever changed the plugs just go ahead and get that done.
Is that a simple enough DIY?

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #7 of 18 (permalink) Old 02-22-2015, 09:27 AM
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Originally Posted by SDpiel8 View Post
Is that a simple enough DIY?
Simple enough because the plugs come pre gapped. Removal of the boot from the plug takes a good pull but rotate as you pull and it will come off.
Don't overtorque the new plugs ( I used AC Delco Iridiums) and use a correct spark plug wrench, supporting the head of the wrench with one hand to keep it lined up square to the insulator or you could break it off. I used a small 1/4" hex knurled head that I fitted a 3/8" drive socket adapter to the 5/8" spark plug socket to hand turn the new plugs in. You want to hand turn anything threaded to make sure that cross threading does not happen before you torque with the ratchet/socket. The stock wires are hardy and well made but I did change mine out to Kingsbornes. You will see a metal ring inside the boot on the spark plug end. Make sure that they are all there. More important to just do the plugs though. When putting the wires on, make sure that everything is clean and avoid getting anything on the insulators. As you are by a location with salt air, dielectric grease can be VERY lightly applied to the inside of the boot if you clean off the old ones with isopropyl alcohol. A super light layer of dielectric grease could also be applied the outside of the wire but I didn't see the need to do that with new ones. Other guys that mod use NGK's and most of that may be because of cams, superchargers etc. The stock number may have changed for the V6 plugs... it did for my GT.

[SIGPIC][/SIGPIC]09.1 G8 GT Sp. Prem. w GXP Facia. Roto Fab covers +chrome caps / Spyder Tail Lamps/VIM Hack c/w rear cam. BMR Sways/ Arms/ Toe Rods/ Rear Cradle Inserts+ Diff bushings/H&R Coilovers / Russell ss lines w CTSV Calipers+2015 SS Rotors . Staggered Avant Garde M310's . KOOKS Mids w HFCs. Corsa w Volant CAI /Dr. Phil 91 Octane Tune on Dyno. RCR Intake & TB/Catch Can w Little Lunati DoD Delete. ZL1 Converter and CNC'd heads by Aggressive Performance MI.
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post #8 of 18 (permalink) Old 02-22-2015, 11:13 AM
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simple as that.
nice, a fellow San Diegan

2009.5 Maverick silver G8 GT
Cunningham motor sports tuned
343HP 349TQ
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post #9 of 18 (permalink) Old 02-22-2015, 11:42 PM Thread Starter
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Ahh ok, I don't trust myself so I think i'm going to buy the parts from autozone and have them installed. I'm not getting a check engine light anymore but it still has a weak heavy engine sound/feel when I start it up.

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #10 of 18 (permalink) Old 02-22-2015, 11:43 PM Thread Starter
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Quote:
Originally Posted by Eloquent View Post
simple as that.
nice, a fellow San Diegan
I've seen several G8s in SD but no members on this site! I always post in the G8's sited thread for San Diego but no one responds lol

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #11 of 18 (permalink) Old 02-22-2015, 11:44 PM
skrt
 
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Im from Oceanside broth
Just up north

2009.5 Maverick silver G8 GT
Cunningham motor sports tuned
343HP 349TQ
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post #12 of 18 (permalink) Old 02-22-2015, 11:51 PM Thread Starter
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Quote:
Originally Posted by Eloquent View Post
Im from Oceanside broth
Just up north
Nice, hella close. What mods you got on your GT

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #13 of 18 (permalink) Old 02-23-2015, 12:21 AM
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Quote:
Originally Posted by SDpiel8 View Post
I've seen several G8s in SD but no members on this site! I always post in the G8's sited thread for San Diego but no one responds lol
Your not alone bro lol
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post #14 of 18 (permalink) Old 02-23-2015, 09:45 PM Thread Starter
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So I had all spark plugs in and they were original from the manufacturer that didnt look like they had been changed in awhile. He said they were extremely filthy. They also found only one coil was bad not two. They just had to clean one up. Car runs fine so far. I'm going to take it out in a little for a cold nighy cruise to see how it does
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post #15 of 18 (permalink) Old 02-24-2015, 01:53 AM
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Quote:
Originally Posted by SDpiel8 View Post
So I had all spark plugs in and they were original from the manufacturer that didnt look like they had been changed in awhile. He said they were extremely filthy. They also found only one coil was bad not two. They just had to clean one up. Car runs fine so far. I'm going to take it out in a little for a cold nighy cruise to see how it does
I am assuming it was the #6 coil. The rear on the drivers side. Mine was changed too. Water seems to get in there. I heard it's common on our V6s.

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2009.1 G8 SV6 Tuned.
Overkill Tune 3rd Gen.
GT Intake system
76mm Throttle body.
X-Pipe,Custom Axlebacks.
3/4" Intake Spacers.
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post #16 of 18 (permalink) Old 03-03-2015, 06:36 PM Thread Starter
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I am assuming it was the #6 coil. The rear on the drivers side. Mine was changed too. Water seems to get in there. I heard it's common on our V6s.
I'm not sure which one it was but the check engine light came back on a few days after install. I was still having the same issue with the engine feel/sounding off after sitting for awhile, especially after a cold night( 50's here). A day after the CEL came on for the 2nd time, the car started to overheat so I pulled over and checked the coolant level and it was fine but I added a tiny bit of water anyways just in case. The engine was cool to the touch too, just slightly warn towards the back as if it were still warming up. I took it into the shop so they could check it out while installing the shotrys and they told me the engine was throwing a ghost code only so they cleared it, left the car running for 3 hours with no CEL or overheating. I get the car back tomorrow so hopefully everything is fine. The tech is going to check out the starting issue in the morning after it sits for the night.

2009 G8 GT Sound&Comfort

Mods:

Drilled/slotted rotors w/ ceramic pads
Solo Axlebacks
Resonator/mid-muffler delete
2.5" H-pipe
Rotofab intake
Dyno tuned at New Era Performance in Socal
-339hp 371tq
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post #17 of 18 (permalink) Old 03-04-2015, 07:49 AM
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Hope its all good.

OGOC Member
2009.1 G8 SV6 Tuned.
Overkill Tune 3rd Gen.
GT Intake system
76mm Throttle body.
X-Pipe,Custom Axlebacks.
3/4" Intake Spacers.
GXP Front Clip,GXP Diffuser.
K&N CAI
Custom Rad Cover.
10" Pioneer Sub and Box.
And More....

[SIGPIC][/SIGPIC]
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post #18 of 18 (permalink) Old 03-04-2015, 09:04 AM
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Thanks for feeding back on that. Another electrical theory goes down in flames for FMQ... I have some stuff to learn from the mechanically inclined folks on this forum.
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