Last post on Aug 05, 2013 at 1:12 PM
You are in the Chevrolet Silverado & GMC Sierra
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Chevrolet Silverado 1500, GMC Sierra 1500, Chevrolet Silverado 2500, Fuel Efficiency (MPG), Truck
#45 of 85 Poor Mileage / surging / clunking / heavy heavy soot and chevy regret
Oct 23, 2012 (5:58 pm)
Purchased my 2011 Silverado 1500 LTZ Crew Cab October of 2011. The first 7000 miles were at 17.7 miles to the gallon. AFM worked perfectly. About 7500 miles the voltage guage started doing the dip below 14v on the guage, and I noticed the trucks mileage started dropping. Then the misshifts, hesitations, coughing, started. I also noticed how HOT my garage was getting after parking the truck in it, you could hear the tinging of the metal cooling down from the exhaust system. I had mentioned the poor running condition to the dealer and was told it was probably bad fuel. I choked on this for a while, and then the soot on the tail pipe started as the mileage dropped. Complained, to no avail, normal normal. .... Labor Day 2012, I bring the truck in and say no more, something is wrong. No codes, but they noticed that the Alchohol content is reading 0% all the time, and the fuel in the truck is 15% Alchohol. They re-learn the Alchohol content, and the truck is normal until the very next tank, which happens to be Ethanol free fuel. Im back to the poor running condition again.
Fast forward to 14k miles. Im down to 13.3 MPG, clunking all the time, and its surging like Im being rear ended. This truck does not like to coast at all, resuming any acceleration causes it to hesitate.
Service department says that they see what my complaint is, but cant fix anything because corporate says its working as designed and wont let them do anything. This "anomale" only happens to be on the 2011 1500 AFM product line. Thing is, they say the delay they put in the accelerator is normal, and its to save all the torque from being dumped on the transmission. Obviously with it the hesitation getting worse, the torque placed on the trans (the clunking), the worse the trans gets.. how is this delay or hesitation helping my transmission again GM ???? 46,000 dollar Mistake is all I keep saying to myself, should have kept the 2006 Ford that got a consistant 15 MPG towing or solo. This is the Last GM product I will ever buy with this kind of lack of integrity from Corporate. Obviously reading here, there are alot of other people that are having the same exact issue with their trucks ...... if anyone is watching, I would love to know what gear ratio the trucks with this issue are equipped with.... Mine has the 3.42's ???????????
#46 of 85 Did they tell you it's normal?
Oct 23, 2012 (8:18 pm)
About 7500 miles the voltage guage started doing the dip below 14v on the guage, and I noticed the trucks mileage started dropping.
The alternator has a energy saving feature that turns it down when the system is not needed.
#47 of 85 Re: Did they tell you it's normal? [chuck1]
Oct 23, 2012 (8:58 pm)
Not needed ??? when has 9V been the same as 12V ??? If you have ever wrenched before, and changed an alternator, battery or starter, you will see that the manufacturer or re-manufacturer states Voltage must be 12.7 for them to guarantee their parts. Starter manufacturers would prefer you replace the battery at the same time as the starter....
Of course its normal, Im well aware of the alternator doing this, we have a 2007 and 2008 3500 Duramax, 2010 1500 LTZ, 2011 1500 LTZ ( this one ) and a 2012 1500 LT, so Im well aware of the issues of these trucks, Im saying that my PCM has probably more issues since this voltage drop, and trust me as much as that needle drops, it also pegs max out to the top of the line they drew so that they dont have to explain this "feature" , they can point and say "NORMAL" just like everything else is "normal"
GM tends to take a great idea and over complicate it. What possible mileage gain can be seen thru turning off an alternator ??? That same gain gets lost when it has to work twice as hard to pump up a weakened battery. Also, my power inverter HATES this voltage drop and will not power up my laptop on trips as the voltage is too low, as it sees that as a battery drain .. Dealer says ... so what, its not our power convertor and wasnt sold as a chevy option......
As a computer technician, I can tell you how many PC power supplies in both desktop and laptop computers I replaced due to faulty power supplies. Problems disappeared once the computer got "clean" stable power. Computers that are underpowered get unpredictable, and you cant tell me an automotive PCM is not the same as a regular computer, its more of a specific task oriented device... but they are pretty much the same animal running on the same 12V DC platform.
What amazes me is, Our $46k cars are not our own anymore, the corporation still owns them and will tell you how they are supposed to run and deny any claim if they can pin it on something else....... In this case, the delay they say should be there is .006 sec upon stepping back on the throttle, and Im saying its a full 3.0 seconds, thats a HUGE difference, one that can be felt most of all about 20- 35 MPH ( school zones, traffic conditions, curvy roads ) and YES, the dealer READ verbatim the blurb from GM about the .006 second delay ...... his response was to stop "tromping" on the gas pedal, well you cant tromp on the pedal in bumper to bumper traffic !!!!!!!!!!!
OH !!!!!!!! yes, I was also told the heavy soot on the tailpipe was caused by a non GM chrome tip on the exhaust, to my reply of - its part of the Z71 chrome package shipped out from the factory with it on.... stopped him dead in his tracks on that, but he said he would check for a "bulletin"
#48 of 85 Re: Did they tell you it's normal? [daninrapidan]
Oct 23, 2012 (9:19 pm)
You should be driving a 1960s model. That way you could change you plugs condenser and points every 12000 miles. Your frustration is you need to buy 100k worth of computerized equipment to work on your truck.
#49 of 85 Re: Did they tell you it's normal? [chuck1919]
Oct 24, 2012 (3:13 am)
We have a G30 old church van, 355,000 miles with a 350, and the old TBI system. 1000 lbs of tools in it, and on regular unleaded its getting 15 consistantly.
The 600$ programmer that will fix the issues, I should not have to spend, as well as violating my warranty. Not for a sticker price on THIS truck of over $46k. To be by the service department and the mechanic that GM has built these hesitations into the sub routine in the computer to "save" the transmission, and the EPA wont allow them to fix it is utter bull ****. Why is my GM vehicle running worse than the first 7500 miles ??
I would appreciate only useful comments on the issue, what or who fixes the problem permanently. At this point, my brother is right, find a decent older truck, and dump 46k into repairs and upgrades and have a real vehicle.
#50 of 85 Re: Did they tell you it's normal? [daninrapidan]
Oct 24, 2012 (6:06 am)
If you're not already working with Customer Assistance and wanted for us to check into this further with you and your dealership, please email us at socialmediagm.com (include your name and contact information, a summary of the situation, the last 8 digits of your VIN and mileage, and the name of your dealership).
Sarah, GM Customer Service
#53 of 85 Re: Did they tell you it's normal? [daninrapidan]
Oct 24, 2012 (8:28 am)
Here is a useful comment for you. Do a search on the internet and find out exactly what the characteristics of these transmissions are. Then, you can make make an informed decision on how to proceed.
1) You can see if others are having the same issues.
2) You can see if they have been able to have them fixed.
It will lessen your frustrations.
I already know the answers to these questions.
#54 of 85 NEW GM TRUCK BUYERS
Oct 25, 2012 (3:52 pm)
Check the transmission forum on this site for very, very similar issues.
Potential General Motors' truck buyers; test drive these trucks extensively at 45 mph and see if they clunk lag growl or bang as the active fuel management moves from 4 to 8 cylinders.
Check for slop in the rear end.
Let us know if you're told "it has to adjust to your driving habits." Right from the GM "play book"!