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Sudden loss of fuel economy - 2014 Chevy Silverado 5.3 LT - dropped 7m


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I'd wait and test this last round first. Give it couple of weeks. Then if bad fuel mileage comes back I'd have a look at the cats. Because you want to know what the solution was.... If you do too many things at once then you don't know what cured your problem just like you don't know now if it was the cleaning or the ebrake that helped.

 

 

My OBDII tool is an APP on my Android called Torque Pro ( $3.99 USd ) best dang $5 I ever spent ( $4.99 Cdn ) You just need a compatible bluetooth adapter and you're good to go.

 

2015-02-14%2011.58.35_zpsuupz6f08.jpg

 

I got this one but get which ever one is compatible with the APP. Some people don't like to buy Chinese but I'm not one of them, they make everything any way so why pay 10 times the price for the same item.

 

http://www.banggood.com/fr/HHOBD-ELM327-Car-Bluetooth-OBD2-Auto-CAN-BUS-Scanner-Tool-Android-p-913030.html?rmmds=search

 

I got a nice cheap BT scanner as well and Torque Pro was the Best $305 I ever spent (I had to buy an Android tablet as well since it doesn't run on iOS)

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UPDATE:I was the orginal poster

 

I have regular 35 mile and 90 mile drives. I still am getting 12mpg @70mph on the freeway. The engine works a bit harder than it should, when accellerating. or getting back up to speed. It only goes into V4 mode downhill and coasting.

 

However, on two trips, I someone got good performance and got 20mpg on my last 25 miles. The engine worked easier and V4 mode was abundant. All in the same exact drive. Getting 13mpg for most, then 21 on last 90 miles. And it was fairly similar landscape the entire drive, fairly flat.

 

On my last trip, I was stuck getting poor mpg, then did an italian tune up and finally got it to go into v4 for some of the trip. Got 20mpg for a little bit, but then now back to poor mpg.

 

*****

Dealer and I think its a coked up engine. It seems like the interminant performance supports our theory. Where there could be some carbon floating around or sticking up the valves still. Next step is for dealer to do their own BG induction cleaning.

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  • 1 year later...

I am having the very same problem.  Did you feel like no one was listening....including your dealership?  A key point to your issue was that you had not changed your driving conditions or behaviour and under the exact same driving conditions and circumstances you had a major drop in fuel mileage.  For me after my first oil change the fuel mileage dropped by 75 percent under the exact same driving conditions.  I got the winter fuel, vehicle idling longer under warm up, lower temperature etc run around as well.  But no one seemed to hear me when I told them that under the identical conditions my mileage had changed drastically.   And oh the other thing, dealer comment that if no engine codes, then no issues!!!!!!!!  and no sense putting on computer.

I commented about air intake sensor or air filter could be dirty as my first thoughts....dealer said no codes no problems.  I don't think no no no problem is necessarily correct.   Dirty Mass Air Flow (MAF) sensor may not throw a code or dirty air filter.....vehicle may still operate within acceptable ranges.  As noted by others in this thread

Winter driving at minus 20 degrees celcius on bare roads with my snow mobile on the back changed from 10.5 litres per 100km to 20 litres per 100 km.

I wrote the above simply to provide history not out of frustration.....and so that others will recognize your mindset....driving behaviour and conditions did not change but significant mileage change...

Did you resolve your problem because nothing has been done for my vehicle yet.....I am still going to take issue with the dealer.  I still believe the Mass Air Flow sensor which is probably the same thing that the BG air intake cleaning and coking aspect relates to possibly, except a comment in this thread about coking seems to imply it is the intakes (lifters) and to put a bottle of intake cleaner through the vehicle (I will be checking into this further after this thread).  Again, hoping you resolved your issue and can get feedback.

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1 hour ago, GM The one said:

I am having the very same problem.  Did you feel like no one was listening....including your dealership?  A key point to your issue was that you had not changed your driving conditions or behaviour and under the exact same driving conditions and circumstances you had a major drop in fuel mileage.  For me after my first oil change the fuel mileage dropped by 75 percent under the exact same driving conditions.  I got the winter fuel, vehicle idling longer under warm up, lower temperature etc run around as well.  But no one seemed to hear me when I told them that under the identical conditions my mileage had changed drastically.   And oh the other thing, dealer comment that if no engine codes, then no issues!!!!!!!!  and no sense putting on computer.

I commented about air intake sensor or air filter could be dirty as my first thoughts....dealer said no codes no problems.  I don't think no no no problem is necessarily correct.   Dirty Mass Air Flow (MAF) sensor may not throw a code or dirty air filter.....vehicle may still operate within acceptable ranges.  As noted by others in this thread

Winter driving at minus 20 degrees celcius on bare roads with my snow mobile on the back changed from 10.5 litres per 100km to 20 litres per 100 km.

I wrote the above simply to provide history not out of frustration.....and so that others will recognize your mindset....driving behaviour and conditions did not change but significant mileage change...

Did you resolve your problem because nothing has been done for my vehicle yet.....I am still going to take issue with the dealer.  I still believe the Mass Air Flow sensor which is probably the same thing that the BG air intake cleaning and coking aspect relates to possibly, except a comment in this thread about coking seems to imply it is the intakes (lifters) and to put a bottle of intake cleaner through the vehicle (I will be checking into this further after this thread).  Again, hoping you resolved your issue and can get feedback.

My dealership did listen, and we did troubleshoot.  They even went as far to pull an maf off a brand new truck and install it on my truck.  Also the put different tire s on.  Different air filter.  A bunch of intake cleanings, which actually burned out my catytyic converter and they replaced that for free.  This took months of troubleshooting, and no help to the 12-13 mpg I was getting in freeway. 

 

I gave up.

 

I sold the truck on Craigslist and paid off my loan. I went and got a 2014 RAM 1500.  I get the 18 mpg that RAM advertises.  At least they are not lying to the consumer.  

 

Been happy ever since.  **** Chevy - they broke my heart.  

 

 

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58 minutes ago, dgrover13 said:

My dealership did listen, and we did troubleshoot.  They even went as far to pull an maf off a brand new truck and install it on my truck.  Also the put different tire s on.  Different air filter.  A bunch of intake cleanings, which actually burned out my catytyic converter and they replaced that for free.  This took months of troubleshooting, and no help to the 12-13 mpg I was getting in freeway. 

 

I gave up.

 

I sold the truck on Craigslist and paid off my loan. I went and got a 2014 RAM 1500.  I get the 18 mpg that RAM advertises.  At least they are not lying to the consumer.  

 

Been happy ever since.  **** Chevy - they broke my heart.  

 

 

You bought a bad truck. My 5.3 gets 22-23 MPG on trips, and at least 16 city. Others I know have similar results.

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1 hour ago, 2017SierraSLT said:

You bought a bad truck. My 5.3 gets 22-23 MPG on trips, and at least 16 city. Others I know have similar results.

You obviously did not read this thread.   I used to get 22 hwy.  And the whole point and conclusion is that I bought a bad truck.

 

But when that's the result, don't tell me you would be willing to take the chance that the next truck will work fine.  That's a big 40k gamble.  

 

And if you are willing to make a 40k gamble, then you probably don't need to care about the mpg.

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1 hour ago, dgrover13 said:

That's a big 40k gamble.  

 

And if you are willing to make a 40k gamble, then you probably don't need to care about the mpg.

It's a gamble when buying any truck. Whether it's buying another vehicle from a brand that you just had a sour experience with or, switching to another brand. I had a 2014 Silverado that had the shakes, switched to Ford and when through 2 (a 2015 Escape, and 2016 F150) that had nothing but electrical issues. So back to GM, been good since. 

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I've always seen 16-17 in my 5.3 (4WD) with 93 tune, but to be fair, I keep my foot in it. I'm curious as to what I'll see after supercharger/new exhaust/AFM delete.

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Tks for response dgrover.

I am surprised by some of the other comments since I posted.  Yes, I have seen people get a lemon, but normally it is a lemon almost from day one.  Again, I mention the oil change as reflecting when I noticed the change in gas mileage.  A year ago under the same driving conditions I was getting 23.5 miles per gallon us.  Now getting 11.7 miles per gallon us.  That's ridiculous!!

 

I was surprised that you said it broke your heart to sell it.  But like you I will trade/sell it if it is not resolved and it will break my heart as well.

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3 hours ago, dgrover13 said:

You obviously did not read this thread.   I used to get 22 hwy.  And the whole point and conclusion is that I bought a bad truck.

 

But when that's the result, don't tell me you would be willing to take the chance that the next truck will work fine.  That's a big 40k gamble.  

 

And if you are willing to make a 40k gamble, then you probably don't need to care about the mpg.

I read it.

 

And yes, I detest the others so bad for one reason or another, I would try GM again. However, I do love RAM, and Ford for one thing: I make huge bucks from them by  repairing those turds for the poor saps that buy them! LOL

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38 minutes ago, GM The one said:

Tks for response dgrover.

I am surprised by some of the other comments since I posted.  Yes, I have seen people get a lemon, but normally it is a lemon almost from day one.  Again, I mention the oil change as reflecting when I noticed the change in gas mileage.  A year ago under the same driving conditions I was getting 23.5 miles per gallon us.  Now getting 11.7 miles per gallon us.  That's ridiculous!!

 

I was surprised that you said it broke your heart to sell it.  But like you I will trade/sell it if it is not resolved and it will break my heart as well.

Actually, we were able to deduce and probably know what it was.  I am not a gear head or expert, but we concluded that the only thing it could be was carbon build up behind the valves.  It's known to happen in all direct injection vehicle s.   Intake cleaner does not work because it doesn't hit behind the valves.  My next step was to pay 1200 bucks to take it all apart and have them clean/replace the valves.  But now you are breaking a number of factory seals and risk other things, just to clean the valves.  Not common for people to do that.  I sold the truck.

 

The only make to solve the problem is Toyota which use a combo of direct injection and fuel injection to keep the valves clean.  

 

Whatever vehicle you run, don't buy crappy gas.    

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A catch can is a solid choice for ANY engine, but more critical for the DI engines due to the aforementioned reasons cited above.

 

I have caught 24 fluid ounces of oily crap from my Elite can in 3500 miles of usage. I put in on my truck at 26 miles.

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