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Discussion Starter #1 (Edited)
Stats: 2008 3.5L Sedan (not GT) 39k miles, bought with 26k and have seen all issues below from day 1 after I bought it.

Hello,

I guess from reading some posts other people have experiences similiar in some respects to mine but I can't seem to find a solution to remedy the issues:

1. Poor idle, rough idle.
2. Slight hesitation on initial throttle application at times
3. Uneven acceleration curve (how to explain in words ... ) Basically the car has the torque of a weak 4 cyl.
- Initial throttle from a stop is lack luster (have yet to break the tires loose with full throttle from a dead stop ever well unless it is wet or icy, and yes with traction control off) actually full throttle starts feel very very weak.
- Through the rpm curve the motor will wane 1k to just under 4k and weakly surge after 4k almost like a turbo building boost but without the actual power. Also at times under acceleration the car will "hiccup" or stutter once and a while.
4. At times it will not kick down (down shift) under moderate load and acceleration with out a heavy foot or manually down shifting. This will cause the car to shudder.
5. Doesn't like cooler weather which is peculiar, the hotter it gets the better it actually runs. Seems to like 90+ degrees with low humidity.
6. Runs the crappiest in the morning after sitting overnight.

What has been done: (All at the dealer)
No codes are coming up
New head gaskets at 33k
Ran "Aphid" test on injectors, all passed
Did a "water/moisture" test on engine compartment did not affect idle.
Fuel system cleaning.

I haven't done anything else yet because I don't want to throw money at the problem and not fix it. The only thing I have done is throw an OEM fit K&N filter in it to try and improve the gas milage.

Any help, ideas would be great.
 

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I'd start by cleaning the air induction system: air filter (already done), MAF sensor & throttle body.

You might pull the plugs & inspect them.

Without looking at the live data, I really don't have much to suggest.
 

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An air injection system cleanup sounds like a really good place to start, As well with inspecting the spark plugs...

When it's nice and hot out and the engine is loving it, does it seem to run just fine? Or is it still kind of on the sluggish side?
I wonder if you have a problem with 1 or more of your catalytic converters...
As your driving does it seem like the longer you drive the worse it gets? Or is it the other way around, Worst at first but gets better as the drive goes on?
If it's the former I'd lean towards getting those cats checked. If it's the latter then that may be a lot less likely.

A dirty MAF could be causing some of the shifting problems. Possibly even more, The computer could be reading less airflow into the engine then what is actually coming through.

A dirty Throttle body can really effect throttle response and overall drive-ability (I have 50k miles and have had to clean it 3 times already)

What kind of MPG are you getting? And also what kind of driving do you do, city, highway, mixed?

Just trying to figure out some pieces to the puzzle to see if we can narrow it down
 

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my 06 g6 gt (3500 v6) gets up and goes pretty good from about 10mph, snaps my head back and the tires kick loose. i also know that right before i bought it, it was tuned up by ac delco.. new plugs and wires and stuff like that, and when in stick mode mines tourqie as hell. but once im past 2nd gear the rpms drop really low and you cant even hear the motor. g6's arent sports cars and werent ment to be. gearing ratios and stuff like that is set for daily wear and tear driving and getting better mileage. not the car to be zipping around in which i do anyways haha
 

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oh and that delay when you smash the pedal down is good, its nothing wrong with the car. my dads 08 vette ls3 does it to and thats only got 6k miles on it.
 

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Discussion Starter #7
Cruisin ... it is hard to explain but typically it is worse from the start and can (can is an iffy word, more like depends on its mood for that drive) improve as I drive. This is mostly from a morning drive, the afternoon drive home after baking in 90 degrees it has a bit more snort right away. Another way I can explain it, I use to deal with hot rods quite a bit and the bigger the cam the less your motor liked lower revs hence drive a stick or use a bigger stall. This is how this car feels kind of, like the cam is too big and you can't get clean power until higher revs, tried to use the turbo and boost example before since it is kind of similar. I can mash the pedal to the floor from a stop or even at 10 mph and it just moves, but doesn't "go". I understand the gearing on these cars were intended to help fuel consumption etc but I had a 99 Grand Am that put you back in your seat and lit the tires up with 130k on a tired 3.4L hehe. Seriously a Yugo could take me off the line. I had it in to 2 different dealers and they are like no codes means no problems but if you want to start throwing money at evaluating it we can do that. This is where I am stuck. I can try the plugs, wires, coil. I have thought about the exhaust as well because this V6 is the oddest sounding V6 I have ever heard. Most V6's have a certain growl to it but this one doesn't. Gas mileage is ok I guess, I drive an 80Hwy/20City to work and back 80 miles round trip. In winter I am lucky to get 20-21mpg but with as hot as this summer has been I have gotten 25mpg. My driving style depends on the a-holes that are around me :) .... I am relaxed with low curteous traffic, and drive like a jerk when people are idiots. So the car gets a full spectrum of driving hehe.
 

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Cruisin ... it is hard to explain but typically it is worse from the start and can (can is an iffy word, more like depends on its mood for that drive) improve as I drive. This is mostly from a morning drive, the afternoon drive home after baking in 90 degrees it has a bit more snort right away. Another way I can explain it, I use to deal with hot rods quite a bit and the bigger the cam the less your motor liked lower revs hence drive a stick or use a bigger stall. This is how this car feels kind of, like the cam is too big and you can't get clean power until higher revs, tried to use the turbo and boost example before since it is kind of similar. I can mash the pedal to the floor from a stop or even at 10 mph and it just moves, but doesn't "go". I understand the gearing on these cars were intended to help fuel consumption etc but I had a 99 Grand Am that put you back in your seat and lit the tires up with 130k on a tired 3.4L hehe. Seriously a Yugo could take me off the line. I had it in to 2 different dealers and they are like no codes means no problems but if you want to start throwing money at evaluating it we can do that. This is where I am stuck. I can try the plugs, wires, coil. I have thought about the exhaust as well because this V6 is the oddest sounding V6 I have ever heard. Most V6's have a certain growl to it but this one doesn't. Gas mileage is ok I guess, I drive an 80Hwy/20City to work and back 80 miles round trip. In winter I am lucky to get 20-21mpg but with as hot as this summer has been I have gotten 25mpg. My driving style depends on the a-holes that are around me :) .... I am relaxed with low curteous traffic, and drive like a jerk when people are idiots. So the car gets a full spectrum of driving hehe.
if i were you id get new plugs and wires. my g6 is abnormally fast. my mom used to have a 2008 g6 v6 and it was a slug. mine throws me and a full carload back in there seats. and i love the way mine sounds, it reminds me of the infiniti g37x's sounds almost exactly alike and has an awesome sound out of first gear especially in tapshift mode, feels like im in a g8 gt (another car i used to drive)
 

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Sound like some similar issues I had with my Cutlass. I got it back to almost great running status when I did a very in-depth throttle body cleaning and replaced the plugs and wires.

It doesn't sound like you have a misfire condition, and I don't think there are very many vacuum lines on the 3.5 aside from the evap system. A vacuum leak can cause a loss of power.

Were you able to pull a spark plug or two to see how they look? Reading plugs is often a great way to see how your engine is running.
 

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Discussion Starter #10
Thanks guys. Plugs and wires was going to be my first effort as well but I figured I would see if there were any other oddities that I could look into before I start just throwing parts at the problem. I will also do the TB cleaning, any recommendations as to how indepth on the cleaining? Buy a spray and just follow the directions? Or get out a tooth brush? I am used to cleaning carbs not TBs and I was once told there is a coating on the TBs that you don't want to mess with.

I am so out of touch with new cars, but it is funny you bring up vacuum leaks because on older cars vacuum was used to help regulate downshifting on automatics. Does the G6 still utilize this? Because my car downshifts decent sometimes and just won't sometimes without mashing it to the floor which would be like the use of a mechanical kickdown.This is on the same drive everyday on the same hills. Sometimes it slips into the half gear, sometimes it chugs and I start losing speed and have to manually downshift or hammer on the gas and it drops to 2nd then back up to 3rd as I lay off the gas. And also if this was an old car I would be looking at the timing advancement, and if it had a vacuum advance like an old car vacuum would again be a place to look.
 

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Thanks guys. Plugs and wires was going to be my first effort as well but I figured I would see if there were any other oddities that I could look into before I start just throwing parts at the problem. I will also do the TB cleaning, any recommendations as to how indepth on the cleaining? Buy a spray and just follow the directions? Or get out a tooth brush? I am used to cleaning carbs not TBs and I was once told there is a coating on the TBs that you don't want to mess with.
Just use TB spray & a shop rag. Then get MAF sensor cleaner & spray the MAF sensor good but don't touch the fine wires with anything but spray. A buildup you can't even see on a MAF sensor can dramatically affect fuel injection system performance.

I am so out of touch with new cars, but it is funny you bring up vacuum leaks because on older cars vacuum was used to help regulate downshifting on automatics. Does the G6 still utilize this? Because my car downshifts decent sometimes and just won't sometimes without mashing it to the floor which would be like the use of a mechanical kickdown.This is on the same drive everyday on the same hills. Sometimes it slips into the half gear, sometimes it chugs and I start losing speed and have to manually downshift or hammer on the gas and it drops to 2nd then back up to 3rd as I lay off the gas. And also if this was an old car I would be looking at the timing advancement, and if it had a vacuum advance like an old car vacuum would again be a place to look.
Modern tranny's are 100% computer controlled & vacumn advance went the way of the Dodo bird long ago.
 

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Discussion Starter #12
Just an update, since I had to pop the hood to replace the battery that died on me today I decided to grab some TB and MAF cleaner. I gave a good cleaning to the TB and MAF and it seems to have helped in some of the aspects. It definitely improved some of the acceleration issues, however it still hasn't improved the throttle response. I was very dissappointed to see that this car is drive by wire, which may be some of my slow throttle response issues. You can't beat a throttle cable for instant throttle reaction. I wonder if the unit on the TB or the throttle position sensor is glitchy, or just overall slow reaction time? Is there any way to test that or wouldn't something like that trip a code?

After taking off the engine cover I am not looking forward to changing those plugs. They are definitely going to be tricky to get to, especially the rear 3. I may just be lazy and pay someone to do those LOL ... It is bad enough having to have an elbow and long extension going through the wheel wells of an 76 TA, but awkward bends and sensitive electronic stuff in the way to boot doesn't trip my trigger.
 

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Discussion Starter #13
Ok after a coupe days of driving, it appears that the stuttering acceleration hasn't gone away. There is more power there but it still has it. It is as if I were letting off and putting on the gas pedal very eradically at times. The car has definite glimpses of nice power more so now than it did before.

Examples now: Driving down the highway ~75 mph, prior to the cleaning I just did. Would have to mash the pedal for the car to accelerate to pass. Now, depends on its mood. At one point I just gave it 1/2 throttle and it launched with out dropping a gear for about 1 second then bogged down then downshifted into 3rd.

When the car is cold it now it really likes to do the "throttle dance" as I will call it from now on where I have it at 1/2 and the car acts like I am tapping out a song on the gas pedal. Again it did this before but now that it seems to generally have more power it is more prevalent so you are getting jerked around in the seat more.

It definitely pulls stronger to 6k now where as by 5.5k it started to wane quite a bit.

Any suggs? Faulty MAF since cleaning it made it better yet worse?
 

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Same Problem?

Mine is sounding like the exact same problem as yours. Do your RPMS bounce at idle? Mine seems to "dance to the music" I was thinking of doing the plugs also at my next oil change, but I'm thinking I might try the cleaning you tried also.
 

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Mine is sounding like the exact same problem as yours. Do your RPMS bounce at idle? Mine seems to "dance to the music" I was thinking of doing the plugs also at my next oil change, but I'm thinking I might try the cleaning you tried also.
How much RPM bounce are you seeing?

Definitely start with the air induction cleaning.

No codes?

Measure the resistance of the spark plug wires end-to-end. Should all be about the same. If one is way high, it's bad.
 

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Discussion Starter #17
Been awhile since I have had time to look on the forums here. Basically haven't had time to do much with the car, have just dealt with it. Yeah the tach on my car will bounce at idle and the car sounds like it has a mild cam in it. And like I said before it acts like it has a big cam in it with the lack of low end power. The car will at times surge with power with no gas pedal change on my part. It is very sporadic when it does it and sometimes when I am not even trying to accelerate hard it just will all on its own with minimal pedal effort. And of course when I want it to it dogs out and pulls like a Yugo. Well until 4-5k rpm then it will pull harder. To try and make the sounds in text it is like 2k .. boowwww .. 3k .... boooowww .. 4k (sometimes with a stutter) ... ba baaaaawwww. And like I said before WOT from a dead stop I may as well Fred Flinstone it and burn rubber with my shoes because this car won't spin the tires unless it is wet or icy. Someday I may try the plugs and wires but that takes cash, and cash has other uses at this point hehe.
 

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Discussion Starter #18
AHA!! ... Well if this is true then this is exactly what I am experiencing! I found this 2007 post on a site called HPTuners.

Quote: "SO I had HPT for my 2k v6 Camaro, but since gotten rid of it and got a 07 G6.


Great car, but these things are "torque managed to hell" Has anyone really started working with these yet on HPT? I know its supported but wondering if anyone has gotten into them.

I have been told, that people are seeing the TB will only open up to 39% below 3k rpms. I it also seems that there is a 1500rpm rev limiter at a standstill. So unable to get a great launch...

I pulled a 15.9 out of the car but I had nearly 2.5 60' with no wheel spin.

Tried with traction control on and off, doesn't make a difference, even tried the low gears as well.


I am just trying to see whats availible in HPT, because don't feel like shelling out $300 (new cable/new license) just to find out all I can do is change some fan settings and a speed limiter, because there are few parameters covered on the 3.5L


also any options for the VVT?" :End Quote

If this is true this is exaclty what I am experiencing with my car. In the back of my mind I was wondering if the TB was opening up to WOT or not. It would also explain the difference in power at the upper RPMS ... This is lame if this is the case.
 

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Hi, y'all! I own an 09 G6 GT 3.5L. Mines having the same issues. I was having a temperature gauge issue where it would not be reading at all and finally got it fixed by replacing the thermostat. That was yesterday, seems to be working so far. Well now, like I said, I'm having the same issues you're having. It's cold here in the mornings and it warms up later in the day to about 60. Well after it sits all night and I use remote start in the morning to warm it up a bit. As soon as I leave it starts doing a stuttering shaking thing at very low RPMs. Like I'm repeatedly pressing on the gas and my RPMs jump a little over 2000. It will continue to do that for a bit until I press harder. It eventually stops after it's at a pretty good running temp. It still feels like it has power, and I can spin the tires a bit at a stop. But early in the morning it just runs really sluggish. Hoping somebody can help me out with this
 
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