[kraddic]

My G6 has 2000 miles on it and I have noticed when the car is in park or neutral I get a slightly rough idle. At times it is worse than others. It also seems to be worse when cold but it is still noticeable at operating temperature. When it is in any other gear besides park or neutral it is fine. I noticed the problem when it had 900 miles on it and I took it back to the dealer that sold me the car. They looked at it and said it was normal to have vibration from the engine. I am a manager at a national auto repair chain and know that it is not normal. I decided not to argue and see if it would get any better but it is still there. I did some research on current TSB's and noticed one on RPM flare and the corrective action was to reprogram PCM. I took it to another dealer and told them about TSB and they updated the software. I thought for sure this would take care of problem, but it did not. Anyone have a similar problem and/or had it fixed. I asked a couple of my technicians that work for me that are ASE Master techs and one guy said he could feel the idle shake slightly as if it was running too lean, but said maybe I was just too picky. The check engine light is not on and I know I am not too picky because the car I had before I got a G6 was a 2002 Grand Am with 22,000 miles and it did not have this problem. Any help or feedback would be appreciated.

Thanks

 

[Fusion]

sometimes mine starts idling rough, but it only does it for a couple seconds. It usually only happens at a stop light. I don't know how to fix it though, i'll just let the computer figure it out since it seems to do a pretty good job the rest of the time.

 

[xtremegrandam]

I've noticed it at times with the G6. I also noticed it on my former 02 SE1 Grand Am. But the 04 GT1 hasnt been doing it yet and its engine is similar.

 

[Shiboo]

Get a lawyer

I have a '06 G6 and I'm having the same issue. It happens anytime the car is sitting still regardless of the gear. It started two weeks after I purchased the vehicle. I took it to the dealership I purchased the car from twice and they just chose to lie to me rather than fix the car. I took it to another dealer and they reseated fuel rail and and replaced the o-ring on injector 6. It ran well for two days and the problem returned. My mileage dropped from 370 miles a tank to 282 miles. I took the car in a total of 5 times and I'm working with a lawyer to get my money back.

My best advice...Track the gas consumtion and start the lemon law process and get your money back.

 

[miscreant]

My best advice...Track the gas consumtion and start the lemon law process and get your money back.

Dang, let's not jump the gun here...

To the original poster: Is the car actually missing, or are you just feeling the engine "bucking" a little (is the idle needle bobbing?)? There are a thousand things that can make one engine feel like it's missing more than another. My 04 T&C really runs rougher than my 01 ever did, but it's not missing on any cylinder and actual idle is not variable. It just happens to be not as smooth. Just about any car will be "rougher" in park than in actual gear with load on it. My G6 feels like it jumps a little at Idle in park. Just because you get some jumpyness in the engine does not necessarily means anything is wrong. I can put a nice steep cam in your engine and make the engine really buck, but there's asolutely nothing wrong.

Go check some other G6s with miles on them and see if they exhibit the same idle characteristics. If yours is significantly different, then I'd press the issue.

 

[MP2]

Dang, let's not jump the gun here...

To the original poster: Is the car actually missing, or are you just feeling the engine "bucking" a little (is the idle needle bobbing?)? There are a thousand things that can make one engine feel like it's missing more than another. My 04 T&C really runs rougher than my 01 ever did, but it's not missing on any cylinder and actual idle is not variable. It just happens to be not as smooth. Just about any car will be "rougher" in park than in actual gear with load on it. My G6 feels like it jumps a little at Idle in park. Just because you get some jumpyness in the engine does not necessarily means anything is wrong. I can put a nice steep cam in your engine and make the engine really buck, but there's asolutely nothing wrong.

Go check some other G6s with miles on them and see if they exhibit the same idle characteristics. If yours is significantly different, then I'd press the issue.

:beer: I agree. Occasionally in park I have felt what I would describe as a stumble at idle, but the RPM isn't actually moving. In fact, come to think of it I haven't noticed it at all in the last 2,000 miles.

 

[ragingfish]

The vibrations are also more noticeable if you're using the A/C or if you have either defrost mode setting on (as these auto-engage the A/C compressor)

 

[kraddic]

Update: I have 9,500 miles on the car and still have, what I feel, a idle problem. When the idle does "stumble" the rpm's do bob up and down slightly. I doubt it has a engine miss because it would most likely trigger the service engine soon light. I have noticed it more with A/C and defrost on too. If this is a normal characteristic of the engine that would be disappointing....

 

[bigbengt67]

No shit the engine changes tone when you turn on the AC (the defroster uses the AC compressor to). The compressor puts a huge load on the engine, therefore slowing it down slightly and changing the tone at idle. Happens in any car.

 

[G6~Mike]

Update: I have 9,500 miles on the car and still have, what I feel, a idle problem. When the idle does "stumble" the rpm's do bob up and down slightly. I doubt it has a engine miss because it would most likely trigger the service engine soon light. I have noticed it more with A/C and defrost on too. If this is a normal characteristic of the engine that would be disappointing....

I have noticed the rough idle since the day i drove mine off the lot. It never stalls and runs fine if you hold your foot on the gas and keep the rpm up a bit higher than factory idle. If you ask me, i think they just set the idle a bit too low for this engine. My 2004 bonnie runs the same way.

~mike

 

[miscreant]

No shit the engine changes tone when you turn on the AC (the defroster uses the AC compressor to). The compressor puts a huge load on the engine, therefore slowing it down slightly and changing the tone at idle. Happens in any car.

As does putting the car in gear as well as temperature. Again, unless I could actually get in the car, I'd never be able to discern what "rough idle" means, it's probably too hard to describe effectively. Many engines these days are designed with piston sleeves that wear themselves in and can lead to some slight erratic idles (the Chrysler engines are good examples).

Additionally, our MAF is located quite a ways away from the TB, and there's quite a bit of tube between the two, which could result in some sensor flux and rough idle.

Are you feeling the rough idle mostly through the steering wheel? does the needle move quite a bit or just a little?

 

[G6~Mike]

When I am at a light I can usually feel it in the wheel and seat. The engine rpm jumps around between 450-600rpm as far as i can tell by the tach. It's so rare that I really dont think twice about it. I have more instances where the car will not shift into overdrive but thats a different issue altogether.

~mike

 

[kraddic]

No shit the engine changes tone when you turn on the AC (the defroster uses the AC compressor to). The compressor puts a huge load on the engine, therefore slowing it down slightly and changing the tone at idle. Happens in any car.

Your right! My RPM's fluctuating up and down is "engine tone change", why didn't I know that. That was the line from the service writer at the Dealership. I have been in the auto repair business for eighteen years, experienced problems with all sorts of models of vehicles and never realized this...........No shit.

 

[miscreant]

Just a couple more things. Since you have been in the auto repair industry for so long, it may be hard not to notice something that would otherwise be thought of as normal.

For instance, I'm pretty sure that the G6 features that same solid engine mounts found in the new 9-3, which has resulted in more felt vibrations from the inherently unbalanced Saab Turbo engines. There's absolutely nothing wrong with the engines, but the solid mounts which provide better chassis response to the engine will cause an increase in felt vibration. The PCM also holds the idle at the lowest point as well. When you shift into gear, you bring more mechanical parts into the equation which can reduce this felt vibration by spreading it out.

You will naturally get some fluctuation in idle, I was referring to it jumping from say 550 to 800 or more, and back. Just sitting, you're Tach should move just a little as the PCM constantly calibrates against the Idle Air table (I don't think we have an IAC motor since we have DBW).

Couple this fluctuation and change in Tone (Tone is the vibration) with an increased stiffness of the Chassis and engine mounts, and you're going to feel the engine more in the cockpit. I can think of few cars with "performance" tuned chassis and engine bays where you don't feel a "lope" in the cockpit.

Ever sit behind an LTX or LSX motor?

 

[White Wolf]

Low idle speed

The tach jump and idle pulse you feel is probably more then likely normal. I have an '89 Ford Probe Turbo GT that idles a bit rough as well. The reason is because the idle is set so low. I inquired about this to Ford and many other mechanics and all said it was normal. Not satisfied I asked other Probe owners and found out the same information.

As long as it is not stalling out I would not worry about it. My G6 does the same thing at idle and yes I watch the tach very closely. My wife cannot see or feel the pulse but I can 100% of the time.

 

[miscreant]

Another thing to consider. Ours is a 60 degree V6, so balance shafts aren't needed. There's a trade-off though. 90 degree V6s with balance shafts, while initially very smooth, tend to get really jumpy later in their life, where as a 60 degree V6 will tend to maintain it's smoothless over the life of the engine.

 

[Shiboo]

There is a recall on the harmonic balancer bolt you should look into. The recall # is Y0042. Unfortunately, my car still runs horribly and I'm still taking legal action against GM. My car vibrates more than my Harley when I'm sitting still and I can't just accept this as normal. I have driven my friends '05 G6 several times and her car doesn't act anything like mine. I'm sorry I bought this car and I won't make the mistake of buying another GM product.

 

[Rich1969]

Rough Idle

I've had this same problem amongst others since day 1.
Dealer now has the car and thinks it's a transmission issue. Car has been at the dealer 5 times now for no starts, tc loss, mph changing to km and other electtrical concerns. My dealings with the GM Customer Assistance number have not been good. GM even sent an engineer twice to work on my car and they still can't say for certain if it's fixed or not. Dealer is to call me early this am to let me know what's going on this time. I was there last night to get something out of the cas as it's been there over a week and they couldn't tell me where the car was.

I loved the G6 until it started with all of the electrical problems. It's only got 4000 mi on it. Told the service director they have until the end of the week and we will either be out drinking a beer or lemonade.

 

[Shiboo]

I’m curious about the fuel mileage. I hit 370 miles on my first tank of gas. Since my rough idle problem started, I’ve been lucky to go 300 miles on a tank. The cars info center says I should be getting 420 miles a tank. Please post your mileage. I want to know if I’m getting the same mileage as everyone else or if this is another sign that my car is a lemon.

 

[G6~Mike]

I’m curious about the fuel mileage. I hit 370 miles on my first tank of gas. Since my rough idle problem started, I’ve been lucky to go 300 miles on a tank. The cars info center says I should be getting 420 miles a tank. Please post your mileage. I want to know if I’m getting the same mileage as everyone else or if this is another sign that my car is a lemon.

My lowest average this winter has been 27mpg. During the summer it seldom drops below 31mpg.
Ranges between 430miles and 510 miles per tank.

Do you let the car idle a lot? 300 mile range is some shitty mileage :agree2: