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2011 Silverado, POOR mileage, surging, no check engine light

77 messages,  Last post on Nov 01, 2012 at 5:57 PM

You are in the Chevrolet Silverado & GMC Sierra Forum.

What is this discussion about? Chevrolet Silverado 1500, GMC Sierra 1500, Chevrolet Silverado 2500, Fuel Efficiency (MPG), Truck

Messages Page 7 of 8

#58 of 77 Brakes by ches31

Oct 26, 2012 (5:06 pm)

I have a 2011 gmc 1500 I have been back 5 times to the dealer for brake problems and truck shaking from the rear. I have had it. I should have spent the extra money and got the ford. I have filed with the state under the law. Nice looking truck but I am done...

#59 of 77 Re: NEW GM TRUCK BUYERS [string2] by chuck1919

Oct 29, 2012 (7:51 pm)

Replying to: string2 (Oct 25, 2012 7:04 pm)
The AFM will not come on well above 70mph. That's about when it cuts off. It will not come on at 75 unless going down a hill.

#60 of 77 Re: NEW GM TRUCK BUYERS [chuck1919] by string2

Oct 29, 2012 (10:26 pm)

Replying to: chuck1919 (Oct 29, 2012 7:51 pm)
Please read my post again,
 
 I went over to the used truck dealer and drove two just like mine. One had 46,000 miles on it, the other 16,000. They both drove just like mine (which is different than the 2011 Silverado Manual explains). It explains that these vehicles should operate in v4 AFM mode well above 70 MPH on flat lever highway, at steady speed without an excessive load (Full details can be found in GM's shop manual)
====================================================
 
My point was that the GM 2011 Silverado Owners Manual does not indicate there is a speed that AFM should quit working. Also, GM's shop manual Document ID # 1995547 explains in detail the parameters for the AFM to work properly. With everything working properly, the AFM should be working if the engine speed is between 700 and 2800 RPM's. That's if you are running on flat highway at a steady speed and not pulling a load. My 5.3 engine turns at 17 - 1800 PPM's at about 70 MPH. Of course, that's in V8 since it won't change into v4 mode above about 65MPH without going down hill or taking my foot off the gas. If I keep it at the hwy speed limit of 70 mph it wont change unless there is a low spot in the road. That's why I'm only getting 16 MPH on the road. The other two used trucks I test drove did not work at 70 miles per hour either.
On the open highway is when the AFM really needs to be working to get the EPA estimated gas mileage shown on the window when you buy the vehicle.
GM had one of their engineers look at my truck and said "it's working normal" and they will not correct it?? BUYERS; LET THIS BE A WARNING, (This problem will not trip a trouble code) MAKE SURE IT WORKS AT 70+ mph BEFORE YOU BUY! If the AFM works at 70 MPH in cruise control on level highway-buy it. It will probably be one that works like it should. The six or seven that I have tested do not. I hear there are some that work like they should.
I have explained the complete details in previous posts.
Mine is not getting any better at 12,500 miles. I'll be trading mine off this week. It's a good truck if you don't mind the mileage, I just can't afford it at 15 MPG City & 16.1 (Pure Hwy miles). Do your homework and Good Luck!

#61 of 77 congratulations by chuck1919

Oct 29, 2012 (11:16 pm)

String
Seriously I am glad you are in a position to finally off load your truck. I know it has been a source of irritation for you. If you don't mind me asking-what will be your next vehicle?
 
I am assuming it will not be another truck because most get no more than 15 or 16 around town and no more than 20 on the highway-since your issue really boils down to gas economy.
 
In addition I have over 3000 miles of open highway cross country trips and 20 mph is very acheivable-but the AFM WILL NOT come on above 70-75mph. I don't care what the shop manual says or your short test drives on the highway. You can validate your decision to trade in your truck anyway you want. The sales tax and license you will end up paying will buy quite a bit of gas-especially considering you obviously are not driving a lot of miles.

#62 of 77 Re: congratulations [chuck1919] by string2

Oct 30, 2012 (11:04 am)

Replying to: chuck1919 (Oct 29, 2012 11:16 pm)
I am assuming it will not be another truck because most get no more than 15 or 16 around town and no more than 20 on the highway-since your issue really boils down to gas economy
 
=====================================================
 
Chuck,
    Thanks for wishing me well. I would not be selling my truck if I would have gotten 20+ MPG as the window sticker showed when I bought it. I normally drive a vehicle for a long time and 15 city and 16 hwy. is no good, too me anyway. That's not what I bought and that's not what I want. As you state above. I shouldn't have any trouble finding one that will get at least 20 MPG on the hwy.
    If GM won't correct this problem, what else will they deny if I have another problem in the future?

#63 of 77 Re: congratulations [string2] by chuck1

Oct 30, 2012 (1:03 pm)

Replying to: string2 (Oct 30, 2012 11:04 am)
String-
Please consider the following:
 
6000/miles a year (assuming HALF your 12,000/yr miles driven will be highway)
 
6,000/miles a year divided by 16mpg=375 gals of gas 375x$4.00/gal for gas=$1,500.00
 
6,000divided by 20mpg=300 gals of gas 300x$4.00/gal for gas=$1,200
Assuming 10 year ownership
 
1,500.00 x 10/years=$15,000.00
1,200.00 x 10/years =$12, 000.00
 
So this is what your talking. The truck is getting it's rated city, you knew that going in. The truck isn't getting it's rated highway (which you didn't know). It looks like an emotional decision-it doesn't pencil out financially-IMHO.

#64 of 77 Re: congratulations [chuck1] by string2

Oct 30, 2012 (6:37 pm)

Replying to: chuck1 (Oct 30, 2012 1:03 pm)
Please consider the following:
  
6000/miles a year (assuming HALF your 12,000/yr miles driven will be highway)
  
6,000/miles a year divided by 16mpg=375 gals of gas 375x$4.00/gal for gas=$1,500.00
  
6,000divided by 20mpg=300 gals of gas 300x$4.00/gal for gas=$1,200
Assuming 10 year ownership
==================================================
 
Chuck, it's not as bad as you are showing
I have been driving my old car instead of the Silverado much of the time. I would normally drive around 15,000 per year. My Silverado overall gas mileage is so bad that it loses around 4 miles per gallon for each gallon used. (sometimes it gets closer to 14 MPG city.)
 
Miles per year - 15,000 16 MPG = 937.5 gallons
                           15,000 20 MPG = 750 gallons
                                                         _____
                                  difference of 187 gallons x $3.50 = $690 approx. per year x 10 years = $6,900
 
That’s roughly $7,000 more for me to drive the same truck you're driving in the same time period. I didn't count on that when I bought it.
However, if I had as much money as you seem to, I might not mind throwing it away for the pleasure of driving this fine truck.

#65 of 77 Re: congratulations [string2] by chuck1

Oct 30, 2012 (7:36 pm)

Replying to: string2 (Oct 30, 2012 6:37 pm)
String-all your driving is not done on the highway though. So you can't figure the total 15,000 annual drivng as being on the highway. The mpg difference is on the highway. So the difference in mpg is on the HIGHWAY ONLY.
 
My mpg in the city will go down to 14mpg under the right conditions. Heavy traffic, high temperature, idling, etc.
 
The sticker for city says 15/city

#66 of 77 Re: congratulations [string2] by chuck1

Oct 30, 2012 (10:48 pm)

Replying to: string2 (Oct 30, 2012 6:37 pm)
6000/miles a year (assuming HALF your 12,000/yr miles driven will be highway)
 
So that $7,000.00 would be $3,500.00
 
If you bought a replacement vehicle for $25,000.00 then at 6% (tax,lic.,etc.) your total will be $3,750.00 in taxes.
 
Where are the savings? We are not even talking about depreciation and such on another vehicle.

#67 of 77 Re: Did they tell you it's normal? [daninrapidan] by daninrapidan

Oct 31, 2012 (6:58 pm)

Replying to: daninrapidan (Oct 25, 2012 6:30 pm)
10/27/12
 
Sold my Silverado back to the selling dealer and purchased a Ford. 16K Loss, but Im happy, and no hesitations / surging. I had a co-worker drive the truck back to Chevy from the Ford dealer, a 42 Mile drive from where I purchased the Ford. He had no idea why I was getting rid of the truck until he drove it. By the time we got there he was extremely annoyed at the performance of this truck, and said he would never buy a Chevy truck after driving this one.

Messages Page 7 of 8

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