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I have a theory my fuel gauge isn't reading accurately. I'm going to have it checked at my next oil change. When I fill up it takes about 13 gallons. How many gallons does it normally take to fill your tank?
 

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Wow. I can't believe the number of people on here who find a rough idle acceptable and just something to live with. You should feel next to nothing on a V6. You can't feel anything in my Honda's 4 cylinder. A V6 should be even smoother, but whatever. Poor idle can be caused by many things. Engine mounts, low idle setting, vaccuum leak somewhere...the list goes on. Find a good mechanic and don't back down. If it truly is caused by bad design then GM should burn in hell for making such a stupid mistake.

Why am I still planning on buying a G6? I think GM did something to my water....
 

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First off, I call BS on the Honda peddler in the previous post. I have driven several late-model Honda 4-cylender and V6 products that have engine vibration at idle, either in-gear stopped at a traffic light/stop sign or parked with or without weight on the parking prawl! The same can be found in Toyota's, Mazda's, Ford’s, GM's, Chrysler’s, Nissan, Mercedes, you name it. You can take any model of car and have some that have zero vibration at idle, and others that have noticeable vibration at idle. It's not specific to any manufacturer, and it's not specific to any model of car. In the late 80's and early 90's, you could in fact define specific models of cars that had chronic vibration due to the engine itself not being very smooth. I'm thinking directly of cars with the first generation V-Tec, GM's classic 2.5L "4 Tech" and the old 2.8L V6 on the A, J and N bodies, Chrysler's Mitsubishi range of 4-cylenders and anemic 3.0L V6 (K-Car’s, Caravan), Toyota's 1.8L (wasn’t that their whole lineup??), Ford's 3.8 and 4.0L sixes, etc etc. With the advancement of technology, engines today shake far less than they did 15-20 years ago. Incidentally, the 2004 Accord I drove to the auction two weekends ago also had a noticeable hesitation for almost 2 seconds when I hit the gas from a stop - cause for concern I would say (Here's the part where I scream bloody murder in fear for my life)! No MIL light. But it's a common problem. And the "V-Tec kicking in..." line is bullshit so don't even go there. Also interestingly enough, the 02-06 Honda/Acura products rolling through PHH seem to have an abnormally high occurrence of paint problems (hoods/bumpers/a-pillars and roofs have more stone chips/paint chipping than any other make and not uncommon to see rust spots on the leading edge of hoods on 02-04’s). More oil leaks at the valve covers than the norm as well. Seems pretty consistent on every 3rd or 4th Honda V6 with over 75,000km. I can't say I care much either for the intermittent harsh 1-2 up-shift on that 5-Speed automatic. Amazing how the 2006’s are still being covered under that secret extended warranty for catastrophic transmission failure that started in what, 2003? Interesting. Perfect you say? I say you're naive and don't know any better. Watch what you write, because you come out looking like a bigger idiot with every post writing stuff that’s straight out of Motor Trend.
 

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From what I've gathered reading the complaints about idle smoothness in gear, in park or on an incline, there are two very different issues here that are being viewed as one. I don’t think that the two distinct problems are actually related and here’s why: There are people that have a vibration when the car is cold and/or when it's on an incline. Then there are people that have a vibration when they pull up to a traffic light or stop sign in gear. These are two different things.

Engines are rotating mechanical components. They will vibrate no matter what. Stick your hand on top of any engine, by any manufacturer, while it's running and you'll feel vibrations. No amount of balancing will completely eliminate mechanical vibration over a broad operating range. Not even the most advanced Northstar V8 or BMW inline-6 will be vibration free to the touch. That's why engines are rubber mounted rather than direct bolted to the structure. I think anyone who’s owned a 1989 Dodge Ram with the Cummins Turbo Diesel can relate to vibrations associated with a direct-bolt mounted engine. Rubber and fluid filled rubber mounts isolate these engine vibrations from transmitting through to the sub-frame, and from there on to the passenger cabin. A number of things will affect the effectiveness of the rubber mounts to dissipate these vibrations from reaching and annoying the shit out of you.

1) When its cold out, rubber becomes hard and less flexible. In idiot's terms, it jiggles less and therefore cannot absorb as much vibration. What doesn't get absorbed is transmitted through to the frame. I’m sure by now you are all familiar with cold weather tire-set, whereby the tires flat-spot and freeze when sitting for prolonged periods in cold weather ( thump thump thump until the rubber thaws, becomes flexible again, and the tire returns to being round). The same laws apply to rubber engine mounts and for that matter, any rubber bushings/fittings. Cold mounts will typically transmit vibration and a slight increase in engine growl/noise. You may notice that when you experience your vibration, the engine noise is a little more pronounced. It may take some time for the mounts to warm up sufficiently to become supple and flexible in the cold.

2) You’re driving a front wheel drive vehicle. The engine in your car swings forward and backward as you drive around. When you're parked on an incline and the weight of the car forces the engine to rotate forward (nose uphill) against the limits of the engine mounts range of travel. What do you think happens? The rubber compresses from bearing the full weight of the vehicle. What happens when rubber compresses? It becomes firmer! And from what you've just learned, as rubber becomes firmer, what should we expect in terms of vibration suppression? That's right! It absorbs less vibration! So when you're parked on the incline and the weight of the car is being absorbed by an engine mount, of course you're going to feel a little vibration! Typically this one will sound like a bit of a rumble. So here's an idea if you regularly park on the incline: Pull into your driveway. Drop the car into Neutral, apply the hand brake, THEN shift to Park. By having the parking brake support the weight of the car, there is no weight on the parking prawl, no rotation of the engine, and therefore no pressure on the mounts to transmit vibrations and noise into the cabin! Please try this and post your results in a new thread.

3) For the older cars in your fleet... what happens when rubber gets old? Think of your house window seals, faucet o-rings, etc. They dry out, crack, and become hard. Where you live will play a huge role in how fast this happens. Again, what can we expect to happen when old rubber mounts become hard and brittle? You lose the dampening characteristics of rubber. A hard, firm object does not absorb vibration very well. Since the old mounts can't absorb the vibration, it is transmits through to the structure and cabin.

4) I wonder what would happen if an engine isn't sitting perfectly square or level on the sub-frame. Say one or more mounts are misaligned and the engine is skewed to the extent that one or more mounts are continuously feeling pressure similar to what you'd come across parked on an incline? You'll get a vibration. What are some other side effects of an engine that isn't sitting quite right or that's moving around too much? Well, torque steer for one! We must have some ex-Ford Taurus and Mercury Sable or Honda Accord V6 owners in here that are all too familiar with their vehicle veering violently one way or another (usually to the right) when they step on the gas. As the power increases, it becomes increasingly important that the engine be mounted square, and that its range of movement is symmetrical. Far from impossible to do but in a world of mass-produced products it's not hard to skew a 500+ pound power train assembly a fraction of an inch to the extent that it may lead to either torque steer or engine vibration in the structure. Food for thought if you are experiencing continuous vibration and/or torque steer and something worth mentioning/forcing your dealer to check.

5) You will ALWAYS experience more vibration with the air conditioning on. Not only does the air compressor place a load on the engine, but you are also contending with the vibration associated with compressing the refrigerant. Mounts can only absorb so much.

Now that you have somewhat of an understanding of how vibrations can be transmitted to the body structure of your car, try this experiment for me. It's a little unorthodox and far from a perfect example but I think it may help a lot of you to understand what happens with picture book clarity. Stretch out your arm and shake your fist vigorously, as fast as you can. If you're doing it right, you'll be tensed up and your fist will only be moving about an inch at a high rate. Feel that? Ok, now repeat the example moving your hand at a moderately slow pace, say about half. Notice the difference? At the slower rate, the momentum and arm shaking is more pronounced and your range of movement is greater. At high speeds, vibration can be somewhat offset by centrifugal force - they can potentially cancel each other out so to speak. Everyone at some point has had an unbalanced tire, and you may recall that the level of vibration associated with it varied as your speed increased. Meaning, you may have felt it stat around 90 (km/hr), peaked at 115, gone at 130, back at 140, intense at 145, less intense at 155, strong at 165, etc. A rotating mass that is grossly unbalanced however will naturally get substantially worse as it accelerates.

Think of how the shaking of your first applies to your car engine: You sometimes feel vibrations at idle -- slow shaking of your first. You don't feel them when you accelerate or operate the engine at a higher RPM -- quick shaking of your first. We've established that the potential for shaking is greater at a low RPM. Everyone's cut their idle RPM operating range down to the minimum to conserve fuel and reduce noise. That automatically increases the risk of idle shake. The computer continuously monitors and adjusts the air/fuel mixture to maximize the efficiency of the engine. That is to say, the optimum air/fuel mixture for your climate and elevation may not result in the smoothest engine RPM. The computer doesn't monitor or care about vibration transmitted to the cabin so it has no way of knowing that a 654 RPM idle is causing a slight shake that doesn't exist at 661 RPM. It doesn’t know and it doesn’t care. As far as it’s concerned, that is the peak efficiency point. While it’s not very easy to nudge up the throttle, your dealer should be able to connect the Tech2 and nudge up the idle speed in diagnostic mode to prove if your vibration is due to low-RPM associated with the air/fuel mixture ratio. If bumping the idle speed a hair causes the vibration to disappear, the tech should be able to trim the fuel mixture slightly to alter idle speed – BUT – I can’t confirm that idle speed is adjustable on the 2005/2006 engines. It was on the 97/98 LA1 (3.4L). It’s food for thought anyway for those of you who feel you have a serious vibration problem. And no, my 2.4L G6 does not suffer from any vibration problems. Of the ones I have rented (all V6), I’d say 3 of the 8 did vibrate a little at idle, intermittently. Ultimately, I think some people are getting a little worked up over it but if it is continuous, I would push your service department to confirm that the powertrain is properly mounted and that the idle RPM is correct.

FYI, I help out from time to time at PHH Fleet Services and I drive several makes of vehicles a couple of weekends a month. These are either new fleet car deliveries or vehicles being returned at the end of their lease. They come back in a whole variety of conditions... ranging from mint to destroyed, aged 3 months to 5 years. Yes, some of the youngest ones are the most damaged!
 

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I know I may be a female and have very little mechanic skills compared to you guys, but I own a 05 G6 with 124,000. Just like you I have had the problem since 20,000 miles. I finally found the solution to the EXACT same problem. Flushing the Throttle body will stop the surge when it idles. I have no clue why this took so long to find or how it finally stopped the problem, but my MPG also went from 29-30 to about 19-20 and the fuel filter was clogged. Replacing this brought my MPG back to a resonable rate. HOPE THIS HELPS SOMEONE!!
 

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I know I may be a female and have very little mechanic skills compared to you guys, but I own a 05 G6 with 124,000. Just like you I have had the problem since 20,000 miles. I finally found the solution to the EXACT same problem. Flushing the Throttle body will stop the surge when it idles. I have no clue why this took so long to find or how it finally stopped the problem, but my MPG also went from 29-30 to about 19-20 and the fuel filter was clogged. Replacing this brought my MPG back to a resonable rate. HOPE THIS HELPS SOMEONE!!
Lol, you just posted on a 5 year old thread.
 

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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).

well in Chrysler Idle speed is automatically controlled by the computer. If idle speed is not correct, the car has a vacuum leak or a sensor problem.



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more Chrysler repair questions
 

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Ok I own a 2006 Pontiac g6 3.5 up until about a month ago I loved this car. I took my car to a local Chevrolet dealership that's approved to do recall repairs. I left the dealership and my car stalled while driving engine reducing power engine disabled. The radio said power steering, car refused to turn over again. I called the dealership the service department was closed. The next morning car started up and i ran a few errands only to repeat the same thing as the day before including the car dealership being closed. Took car in to dealership after calling and talking to dealership car died at bay doors. I got a call from the dealership saying it was my battery and that a new battery would cost $120. I picked battery up and took it back to where I bought it from had it tested battery was GOOD. Went back to dealership battery was retested in front of me now battery was GOOD. I'm having my time wasted and car killed by taking it in for recall repairs. DON'T DO IT! If GM had any honor they would pay and remove all of these from the road. I'm at a loss car at dealership and I'm stranded. :-\
 

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Ok I own a 2006 Pontiac g6 3.5 up until about a month ago I loved this car. I took my car to a local Chevrolet dealership that's approved to do recall repairs. I left the dealership and my car stalled while driving engine reducing power engine disabled. The radio said power steering, car refused to turn over again. I called the dealership the service department was closed. The next morning car started up and i ran a few errands only to repeat the same thing as the day before including the car dealership being closed. Took car in to dealership after calling and talking to dealership car died at bay doors. I got a call from the dealership saying it was my battery and that a new battery would cost $120. I picked battery up and took it back to where I bought it from had it tested battery was GOOD. Went back to dealership battery was retested in front of me now battery was GOOD. I'm having my time wasted and car killed by taking it in for recall repairs. DON'T DO IT! If GM had any honor they would pay and remove all of these from the road. I'm at a loss car at dealership and I'm stranded. :-\
Good afternoon brownfoxx,

I truly apologize for any inconveniences associated with your recall. My team would like to look further into this. Please PM us with your VIN so that we may assist from there.

Regards,

Amanda K.
GM Customer Care
 

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The common problem with most GM vehicles is the passlock also known as VATS.
Next time this happens. Check the DIC for either a flashing or solid red lock. If it's lit then this is the issues.
 
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