|07-09-2013, 06:16 PM||#1|
Join Date: Jul 2013
2007 Vue Hybrid MPG Rollercoaster
After unsuccessful services by mechanics and no having any luck in trying to track down the problem with our 2007 Vue Hybrid, I am hoping some knowledgeable forum members might be able to provide some insight.
We purchased the Vue (2007 GreenLine/Hybrid) for my wife last April (2012) from a dealership in Florida and drove it back to Texas - over a 1000 mile trek. It had around 70,000 miles on the odometer at the time. For the whole trip, the car performed flawlessly and averaged 30-35 mpg tank after tank of gasoline. Upon arriving back in Texas, we noticed to gas mileage begin to slip after several months, slowly tapering at first (~25 mpg highway) and then drastically dropping (~18 mpg highway).
Initially, we assumed the stop-start city driving to be a contributing factor, but after the sharp dip, we looked at other options. We changed the air filter and had the fuel system treated for deposits possibly knocked loose by the long drive. The cold winter was the next suspected culprit for poor mileage, now near 20 mpg. When warm weather returned with no change, we took the car in and the codes pulled (not engine fault codes/engine warning light codes). The service center mechanic said it was faulty fuel injectors, and that his database said they were a common component to fail with this model. We had them all changed and the performance improved instantly - 24 mpg highway and smoother idle. We thought things were on the up and up, heading back to the glory days of 30+ mpg.
Now, however the gas mileage has again plunged (~18 mpg highway), and the idle will occasionally be rough. Also, when trying to go up the slightest incline the accelerator must be pushed to the floor and power is almost nonexistent. During cruise control, the car will fall several miles below the set point and then kick on, revving the rpms drastically and increasing the speed to 5+ miles per hour faster than the set point before calming down - even on a flat road. The Eco light seems to appear less frequently, and the Auto Stop also seems to be decreasing in duration (even with air conditioning off). It seems like performance has been decreasing every day for the past few weeks.
We don't know what to do - the service center doesn't have anything concrete, just more "options" to try. Has anyone had any similar experiences? Any ideas on where to go from here?
Thanks in advance for your help.
Note: The car now has about 75,000 miles on the odometer.
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|07-09-2013, 11:06 PM||#2|
Join Date: Oct 2008
Location: Cedar Rapids, IA
2005 VUE 3.5L
2007 VUE 3.5L
Re: 2007 Vue Hybrid MPG Rollercoaster
One of the GL folks will most likely offer valid suggestions ... but until they come on-board I'll offer a few thoughts.
To be sure I understand - are you currently experiencing any check engine or reduced power indications?
If I were to offer a guess I'd lean toward something fuel related - either fuel pressure, quantity delivered to engine, or quality of fuel you put in the Vue.
I've attached a service manual extract for many symptoms ... repost if you'd like to have any of the docs listed in blue.
The ECM (engine control module) determines how rich to make the fuel/air ratio based on several sensors - with much weight given to 02 sensor located ahead of the catalytic converter.
There are probably a dozen or two malfunction codes for a bad O2 sensor but we know they can go haywire and skew the fuel mix (lean to rich) and never set a code.
The ECM determines engine RPM by sending commands to a small motor attached to the throttle body. Demands are sent to ECM either by the foot-feed or internal cruise control circuit. You say the cruise can be flaky but do you notice poor throttle response when using gas-pedal?
If yes ... inspect the throttle body for deposit buildup around the butterfly valve. A gunked butterfly might be offering too much resistance to the drive motor resulting in poor throttle response (most noticeable using cruise).
I try to visit forum often but suggest you use private messages if in a rush (comes to cell) and include email address for extracts. I seldom check visitor messages so please don't use.
|07-12-2013, 10:57 PM||#3|
Join Date: Nov 2004
Location: Seven Valleys, PA
2008 Astra XE
Re: 2007 Vue Hybrid MPG Rollercoaster
Interesting issues you are reporting. I can't say we've experienced the same, but I may be one of the few GL owners that still frequent these forums (and still, less frequently than I used to).
We are approaching 100k on ours, purchased new, and the performance and MPG is still fairly consistent. When we moved and our commute changed, so did the mileage, but a recent highway trip got us more than 32 mpg with a family of four aboard, so we're still in the ballpark.
Lots of factors can affect MPG, but what you're experiencing is certainly drastic. We never see mpg below about 25, even in winter with mostly city driving. It certainly sounds like something is amiss, but it's curious that the SES isn't illuminated. Here are a few observations about your issues:
1) Cruise control sucks on this car, period. It will happily struggle in 4th for a while, drop two gears and zoom past the setpoint, wasting gas in the process. Our mileage with cruise is far worse than without it. I avoid it.
2) Your tech is right; the injectors are a known trouble spot with the 2.4L engine (same issue affects HHR, G6, etc). There is a TSB that instructs techs to replace all four when one is determined to be bad. This usually is accompanied with the SES light, and it's happened to us twice (both under warranty).
3) As far2grumpy mentioned, a throttle body service is a good idea. We had it performed years ago (when the dealer was still around) and I think it cost $45. It was the only out-of-pocket, non-maintenance repair we've ever had on this vehicle. I agree that this sounds like a fuel related issue, but it's curious that there are no codes set.
4) Auto-stop should last 2 minutes when the vehicle is warm (w/o AC), so if it's much less than that, there may be an issue with the hybrid system. This is under warranty for 8 years or 100k miles, so you're still covered. There have been 3 recalls that have affected the hybrid system on our '07--have your VIN checked to make sure all have been covered. Your local Chev dealer should be able to do the work.
Good luck and keep us posted. I hope it works out for you. We've really enjoyed our VUE GL for the past 6 years.
Former: 2005 L300, 2007 VUE Green Line
Current: 2008 Astra XE
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