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Discussion Starter · #1 ·
We have a G6 GXP as specified above and it stutters/jerks at 40-55mph... I can not find a straight answer on the internet, and from what I seen neither has anyone else so I am trying my luck here. When driving under 40 or over about 55 it does fine its between 40-55 it starts stuttering really hard.. from what I've seen it could be anything from bad spark plugs to being in need of a tune up or software update... has anyone been able to confirm or deny this?
 

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Is the CEL illuminated, any codes?
Start at the basics, you mentioned.
When were the plugs done last?
If you can't remember, change 'em then move from there.
It doesn't make sense to diagnose a vehicle that needs basic maintenance.
Probably wouldn't hurt to do the wires while you are at it.

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Discussion Starter · #3 ·
Is the CEL illuminated, any codes?
Start at the basics, you mentioned.
When were the plugs done last?
If you can't remember, change 'em then move from there.
It doesn't make sense to diagnose a vehicle that needs basic maintenance.
Probably wouldn't hurt to do the wires while you are at it.

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The code that I can pull is one for high purge flow, only other light than that is the tire pressure monitor indicator. I took it to the shop yesterday and they couldn't quite figure it out either. We just bought it a couple weeks ago so I'm not sure when the plugs were done last so I didn't want to throw parts at it without getting some reliable insight first with so many possible causes and the amount of people across the internet I've seen have this problem I figured someone might be able to narrow it down a little more. Unfortunately since we weren't able to get on the highway or drive it very far (they sent us on a test drive with no gas) we weren't aware of the problem until after we had bought it. I will look into starting on the plugs first though, probably the least expensive of the "probable causes"...
 

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Posting the actual P _ _ _ _ number will give members here a clearer picture to offer advice. BUT since you say a code for high purge flow rate, it's quite possible that the purge control solenoid on the engine is stuck open(and rather common on all GM older vehicles). Not an expensive part or hard to replace.
Stuck open acts as a vacuum leak and can cause some of your problems. Just getting a used vehicle, should have planned to do spark plugs and wires right off as these are 2 of the most overlooked maint. items of any car.
 

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We have a G6 GXP as specified above and it stutters/jerks at 40-55mph... I can not find a straight answer on the internet, and from what I seen neither has anyone else so I am trying my luck here. When driving under 40 or over about 55 it does fine its between 40-55 it starts stuttering really hard.. from what I've seen it could be anything from bad spar
We have a G6 GXP as specified above and it stutters/jerks at 40-55mph... I can not find a straight answer on the internet, and from what I seen neither has anyone else so I am trying my luck here. When driving under 40 or over about 55 it does fine its between 40-55 it starts stuttering really hard.. from what I've seen it could be anything from bad spark plugs to being in need of a tune up or software update... has anyone been able to confirm or deny this?
k plugs to being in need of a tune up or software update... has anyone been able to confirm or deny this?
I own an 09 G6 GXP and my car has a nice take off until 30mph and at that point it does the same as what you're describing except after 40mph it runs nice and smooth! So from 30 to 40 it hesitates or boggs down and after 40 it has no issues. I've had a complete tune up and replaced all the belts! Thought it was one of the gears in the transmission so I had it looked at by 3 dealerships, one which sold new Pontiacs for years, and everyone told me my car was perfect! Transmission is fine! Engine is great! I drive a lot for my job and I know there is something not right.
 

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My 2008 GT 3.5 V6 with 106K does the same thing when under a load at 42 - 45 mph. If you step on the gas it goes away. If it shifts down into 3rd gear it goes away. This weekend I'll be changing the plugs and wires to see if it fixes it. I'll post the results. I so had the CEL come on once while doing this today but it went right out and no code on the computer.
 

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My 2008 GT 3.5 V6 with 106K does the same thing when under a load at 42 - 45 mph. If you step on the gas it goes away. If it shifts down into 3rd gear it goes away. This weekend I'll be changing the plugs and wires to see if it fixes it. I'll post the results. I so had the CEL come on once while doing this today but it went right out and no code on the computer.
Yesterday I changed the spark plugs in my car. I didn't change the wires because they look fairly new. The big laugh was that plugs 2,4,5,6 all came out by hand. Yup, loose as could be. While doing these I noticed that the MAF looked filthy. I sprayed that all out with MAF cleaner and took the car for a ride. There is no more stuttering at 42 mph like it did before.
 

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Yesterday I changed the spark plugs in my car. I didn't change the wires because they look fairly new. The big laugh was that plugs 2,4,5,6 all came out by hand. Yup, loose as could be. While doing these I noticed that the MAF looked filthy. I sprayed that all out with MAF cleaner and took the car for a ride. There is no more stuttering at 42 mph like it did before.
The stuttering is back. There are no codes. I did have a po420 a few weeks ago and another one yesterday. The cat conv. Is not plugged up. I guess the stuttering could be pulling the po420 code. Does this car have an electronic throttle? I haven't had time to look at it recently. My guess is that there is a bad potentiometer if it is electronic. The stuttering is always around 1200 - 1500 RPMS when barely stepping on the gas. I'll try spraying down the MAF again today to see if it helps. My car was running well after I did this the last time. It seems to be doing it more frequently now.
 

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My car does have an electronic throttle. I reset the throttle by turning on the key and slowly depressing the throttle and releasing it slowly. The car was fine for 35 minutes and started bucking/skipping again at low rpms. Time to check the switch. I also have no codes but show a heater light on for the oxygen sensors. Maybe that is causing this.
 

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My car does have an electronic throttle. I reset the throttle by turning on the key and slowly depressing the throttle and releasing it slowly. The car was fine for 35 minutes and started bucking/skipping again at low rpms. Time to check the switch. I also have no codes but show a heater light on for the oxygen sensors. Maybe that is causing this.
Yesterday I reset the throttle switch again but moved the pedal much slower than the day before. I went for the same ride I did on Thursday and my car is not acting up.
 

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Glad that you are finding solutions to your issues. There have been threads on cleaning the throttle body as well as the idle / tps relearn. If it happens again, it might be worth a clean.

Hope it stays fixed
 

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Glad that you are finding solutions to your issues. There have been threads on cleaning the throttle body as well as the idle / tps relearn. If it happens again, it might be worth a clean.

Hope it stays fixed
It is just starting to warm up in the Northeast. This will give me more time to dig into it if it doesn't work out. I also know the heater on the 02 sensor is supposidly not working but my code reader has checked them all out as okay. That is another weird problem.
 

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It is just starting to warm up in the Northeast. This will give me more time to dig into it if it doesn't work out. I also know the heater on the 02 sensor is supposidly not working but my code reader has checked them all out as okay. That is another weird problem.
The problem is back again worse than before. It is doing it in all gears at that rpm. I'm going to clean the throttle body this weekend. I have 4 new 02 sensors on the way. That will eliminate one item.
 

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The problem is back again worse than before. It is doing it in all gears at that rpm. I'm going to clean the throttle body this weekend. I have 4 new 02 sensors on the way. That will eliminate one item.
I installed 4 new 02 sensors. I took the car for a 50 mile ride and the stuttering was gone. The car's gas mileage shot up to 36 mpg. I was driving a constant 45 - 50 on country back roads. The next day I took the car into the city and the stuttering came back. The gas mileage settled out at 26.8 mpg from the country into the city and back home. My car was averaging 21.3 over the past few months. I gained just over 5 mpg by swapping out the 02 sensors. My previous best highway mileage was 27.3 mpg.
 

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I installed 4 new 02 sensors. I took the car for a 50 mile ride and the stuttering was gone. The car's gas mileage shot up to 36 mpg. I was driving a constant 45 - 50 on country back roads. The next day I took the car into the city and the stuttering came back. The gas mileage settled out at 26.8 mpg from the country into the city and back home. My car was averaging 21.3 over the past few months. I gained just over 5 mpg by swapping out the 02 sensors. My previous best highway mileage was 27.3 mpg.
I also cleaned the MAF and throttle body. I'm leaning towards a EVAP leak now. I have a red light on my scanner for it now.
 

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I also cleaned the MAF and throttle body. I'm leaning towards a EVAP leak now. I have a red light on my scanner for it now.
I'm really invested in your journey fixing this issue. My 08 G6, 3.5l is staring to do the same things. I'm gonna take a look at those solutions as well, if I can get it to work I'll post it here. Good luck!
 

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I'm really invested in your journey fixing this issue. My 08 G6, 3.5l is staring to do the same things. I'm gonna take a look at those solutions as well, if I can get it to work I'll post it here. Good luck!
This issue has driven me crazy. It comes and goes along with the check engine light. I also notice that my obd scanner shows a red light on it for the cat. conv. plus 2 other things when the check engine light is off. the engine light goes on, the other 3 lights turn green and the evap light comes on red. I have been so busy that I have been ignoring it for now. The evap switch had a bad connection on the motor switch. I have that working now. I think the problem now with the evap is the valve on the tank. I need to check that out next. I hope you can figure out what your problem is. It is definetly in between the 1200 to 2000 rpm range at any given speed or gear that I am in with a slight bit of load on the engine. A little more throttle or a downshift and it goes away immediately. My obd scanner shows that my Cat. Converters and 02 sensors are working fine. Another thing I have noticed is that if I do a gas pedal reset that the bucking goes away for a few drives while it relearns itself.
 
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