MPG problem

[Jayco]

Hello everyone. I've been reading the forums looking for someone to have the same issue I have, but no joy.

First, I have a 2012 1.4 sonic 4door sedan. It has 17,000 miles on it so far, and I hope to double that in the next six months. My driving is not granny, but it's not aggressive either.

Interstate driving is normally cruise control on, locked in at about 74 MPH, and we are in flat country at sea level. Hot, so the AC is always on. Humidity averages about 85%

Local driving is standard start/stop between 35 and 50 MPH. About 50% of my driving is local at the moment. I'm fast off the start, but not flooring it - mostly keeping with traffic.

I'm averaging about 30MPG city, and about 34 MPG highway - and my gauge is always wrong on the high side. Sometimes as much as 15 MPG wrong.

Factory setup, no mods.

Here's the issue.

The car runs rough at startup - but not all the time. It never throws a code.

Sometimes it's smooth as silk and the MPG will climb to 45MPG by the gauge, (reality is about 36 MPG) and it will just be like the engine isn't running. Other times, it seems to be struggling.

I've discovered that when it's running smooth, and I exit the interstate by just pushing the clutch in and coasting off, the motor will die. I'm not even aware of it until I am ready to take off and no power.

But the most annoying problem, is that on occasion, it sucks gas like a... something. I will go less than thirty miles and go through a quarter of a tank. It runs rough, has no power, and seems sluggish. No code, no smoke that I'm aware of.

Taking exactly the same trip on two different days I got this...

First trip was under a quarter of a tank from full. 150 miles or so. Average speed is about 65 MPH.

Second trip will cost me more than half a tank, same 150 miles, and same average speed.

I made a trip two hundred miles from home. On the outgoing leg, I was at one bar over half a tank. On the return leg, I was at 1/4 tank when I got home.

It's driving me batty!

Aside from running rough and occasionally dying, the only other issue is that in first and second, if I'm gunning it a little, the power is low and then peaks quickly... in other words, I can press the pedal down, and it will bog down a little, then surge in power for a few seconds, then at the top of the power range it will fade out. That hesitation between the kick off and the surge makes me wonder of the turbo is binding somehow.

The dealership had been 0 help.

Thanks in advance.

 

[Preloader]

Check your spark plug gaps. They are very inconsistent from the factory.

They should be .028". If that doesn't solve it, I would lean towards a faulty fuel injector. They are very easy to change. If you can find a good price, I'd give it a shot.

Technically the dealer should fix this for free. If your local dealer isn't helpful, you may try a another one.

The dealer 20 miles from me is FAR SUPERIOR in service and attitude than the one 2 miles away that I bought my Sonic at.

 

[Jayco]

Would a fuel injector cause a code?

 

[Chevrolet Customer Care]

Hi Jayco

You are still under your Bumper to Bumper warranty. I would suggest that you take the vehicle to a Chevrolet dealer. A diagnosis is an important part in determining the cause of your inconsistent MPG concern. Let me know if you would like for me to locate a dealership in your area.


Jackie
Chevrolet Customer Care

 

[Preloader]

Would a fuel injector cause a code?

Not necessarily. I had a bad one, and even though it idled like hell, it didn't throw a code for months.

 

[Jayco]

I took it to three different dealerships.

Dealership one did a mileage test that said that I was getting 59 miles to the gallon. They also told me, "No codes, we have no idea what to do, drive it until it breaks."

The second dealership called me a liar. No, really, they just called me a liar. Said that the mileage display in the computer is always accurate, and that I was making a mistake somehow. They were really nice when they asked me to leave.

The third mirrored the first in that they put it on the computer, said all of the trims were in range, and that they have to catch it doing the problem before they could fix it.

The problem is not consistent. I can do an 800 mile trip and not have it happen at all, and then do a return leg and it only happen once. And before you ask, I have good reason to not consider bad gas.

A bad injector sounds plausible. I was also wondering if the turbo could be binding.

 

[sx sonic]

Do you have an ultragauge or something to monitor boost and/or fuel trims?

You may have a bad injector or the wastegate shaft could be binding (there's a bulletin on it). The WG binding has been pretty rare and it appears to take awhile to throw a code and is also intermittent.

I'd also recommending staying very, very far away from that second dealer. That's a poor attitude and to say the DIC is always accurate is moronical at best.

 

[Jayco]

Do you have the number to that TSB? I've looked and not been able to find it. It would explain nearly everything I've run into.

 

[Preloader]

Do you happen to know if your exhaust gets smokey when the problem arises?

These 1.4's are sensitive to an unsealed crankcase. Ex: oil cap not sealing, dipstick not seated all the way.

I'm reaching, but also genuinely trying to be helpful. There have been a few with similar symptoms, and when we brought up the cap and dip, they had a revelation, went out and fixed the issue for free.


Intermittent makes for the worst kind of troubleshooting. And frankly, a bad injector is usually not intermittent.

Does the problem last long enough for you to stop, pop the hood and investigate while its happening or is it gone as quick as it comes?

Intermittent is usually associated with loose electrical connections. Maybe at the TPS (throttle position sensor) or at the ignition coils.

 

[ranvette]

I have seen bad valve covers cause similar problems.I would make sure it has the latest design valve cover.I would also have the dealer start a case with GM Tech section on it.That would be the first thing i would do.They may have other cars doing the same thing.GM will also send out a field engineer to assit the dealer in fixing it if need be.

 

[Crazzyboy]

So your saing your getting 34 mpg WITH : 1. 74mph 2. AC on AND 3. 85% Humidity? Hell thats good!
AND 30 mpg city? same conditions? Thats Fantastic!!!!
With Same city conditions minus the humidity I can only get 29 maybe 30 babying it. Not sure why you are complaining as that is pretty dam good. Not sticker I know, but still good for the conditions.
And yes the mpg calcualor in the gauge is horribly wrong. And dealers do suck.

 

[Jayco]

Consdiering that the sticker says 36 city, and 40 highway.... I think you have something wrong with yours.

 

[Crazzyboy]

Consdiering that the sticker says 36 city, and 40 highway.... I think you have something wrong with yours.

Oh right, I forgot the Government and Big Corporate Businesses never lie. Did you fail to see the window sticker disclaimer of "actual results may vary"? You do realize that the tests are run in a laboratory under more or less ideal conditions? That is, if they are run at all. Sometimes they just get the math geeks to calculate it all out on paper. I had pretty high hopes for the Sonic myself, but getting 35-37 doing 80+mph is fine by me

 

[Macehammer]

Oh right, I forgot the Government and Big Corporate Businesses never lie. Did you fail to see the window sticker disclaimer of "actual results may vary"? You do realize that the tests are run in a laboratory under more or less ideal conditions? That is, if they are run at all. Sometimes they just get the math geeks to calculate it all out on paper. I had pretty high hopes for the Sonic myself, but getting 35-37 doing 80+mph is fine by me

I get 35-40mpg in my RS. I understand the 1.8 doesn't do well, but i believe the reports I see of the "terrible" mpgs some are reporting are a combination of a few varying factors.

1.) The inability to drive for economy. Some people call this lead foot, but it can be as extreme as what I call "Erratic stupid driving."

2.) buying crap gas.

3.) a fluke car, that doesn't get nearly the mpgs most people are reporting when they drive like a grandma.

 

[Jayco]

I get 32 normally with average driving WHEN it's working right. That's a mix of city and highway. Highway I have rarely seen anyone over 36, (one time was when I was in the mountains and driving really aggressively, playing the curves and squealing the tires - and I got 42 all day that day!) But if it's just city, then 24 to 26 mostly. And no, I don't have a lead foot. I drive with traffic mostly. Easy starts, easy stops. If I drive like a rae-car-driver wannabe, then I'll get a whopping 23MPG.

Day before yesterday it did it again.

Everyone in the car noticed that it seemed to be lagging and had no power. It was sluggish, no white smoke, but when you accelerated the lower half of first gear was bogging down, then about 3K RPM it would surge and shove us back into our seats. Really unpleasant drive. Same position on the pedal and always from a dead stop.

I hate this damned car. I loved it for all of about a week. Until that first time it went through quarter of a tank in about twelve miles.

And the dealership? I called the 1800 customer number and tried to get them to trade mine out with a different car, or give me credit on a new one, and they laughed at me, LAUGHED at me! They said, and I quote, "We are not going to do anything to help you get out of that car!" She was a snotty disaster! After about fifteen dealership visits in four states, I'm ready to just set it on fire somewhere.

 

[Crazzyboy]

one time was when I was in the mountains and driving really aggressively, playing the curves and squealing the tires - and I got 42 all day that day!
Everyone in the car noticed that it seemed to be lagging and had no power. It was sluggish, no white smoke, but when you accelerated the lower half of first gear was bogging down, then about 3K RPM it would surge and shove us back into our seats. Really unpleasant drive. Same position on the pedal and always from a dead stop.

Ok So with your Mountain drive, you got 42 combind up and down the hill? As you probably were getting something like 10 going up, and 100mpg on the way down.
So on with your second complaint of extreme turbo lag. Where are you? Driving around Vegas at about 2200 feet above sea level I know exactly what you are talking about. Worse when its really hot(has its been hot latley). When I drive back to California at Sea Level, the turbo lag goes away completly. In other words it has a more consistant powerband, rather than the lag lag lag till 3k then throw your head back.

I am only trying to help you understand the physics of your frustrations here. I am by no means a genius, but I fought and fought and fought a good friend of mine about altitude does not increase turbo lag. Finally had to admit he was right when I experienced it myself

 

[Jayco]

You know, that's the funny thing...

I get the lag at sea level. I live in Florida almost at the ocean. The really great mileage was in Kentucky at 4K feet. It ran great there, mostly, except that time it used a half tank between rest-stops (about 50 miles)

Here, sea level, average 85% humidity, temperature hovering about 85-90o

But honestly, I'm not overly concerned with mileage. It sucks - and I bought a Government Motors Car. I deserve what I get.

The issue I am mostly concerned with is the sudden heavy gas usage. Imagine, I'm heading to Alaska, where there isn't any fueling stations for a hundred miles at a time - and all of a sudden this POS decides to empty half a tank of fuel and I don't notice it happening. A 50 mile walk back is NOT my idea of a great vacation.

I've already determined that it's not reliable enough to take on really long trips, but my alternative is a truck that's damaged at the moment... and it gets 25 MPG highway all day long in nearly any terrain. (6.5 turbo diesel)

So the issue is that I can drive a 1200 mile trip, and it will average 34-36MPG by the lie-o-meter, then, with no warning, I'll notice that it seems to be lagging a little - no sudden start, just seems to gradually lose power, and I'll see that I am burning fuel at an alarming rate.

The only code it has ever set was once in the Smoky Mountains, something about the MAF sensor (or something like that) not compensating fast enough... when THAT happened, it set a code and the turbo just quit. I was lucky to have made it to the rest area on that one.... that's a nasty stretch of road.

The only symptom that I see is that the turbo seems to be spooling up too slow sometimes, but not all the time.

The damned dealership says that they can't even look at the turbo without a code.

 

[River_Rat]

I love driving around Kentucky at 4000 ft.

 

[Jayco]

Why are you rolling your eyes? The summit of Black Mountain, just north of Cumberland Kentucky, is 4,145 feet high. Pine Mountain is 3,275 feet at the top, and you have to go near the top to get to Hazard, which is a little under 1K feet on the other side. Leslie County tops out at 2600 feet, and drops to 980 in Hyden.

The back roads from Pineville to Hyden, the Fun Drive, are mostly two lane and you need to know how to get over for the coal/logging trucks.

What was so sad was that I haven't been there in so long, that I was getting passed by pickups, and I was going as fast as I dared. I felt like a tourist!

 

[Macehammer]

If your car is throwing codes, you need to see somebody, especially if you are not tuned.

I would get in contact with another dealership, or try getting into a convo with the Chevy support ppl on this site.