[nbrown0529]

Hello all,

I am a little new to the forum group but I am hoping to spark a conversation about the fuel economy on my 9th GEN Malibu.

Vehicle Info:
2016 Chevrolet Malibu 1LT w/ 1.5L Turbo

EPA states this car to be 27 City / 36 Highway & 30 MPG Combined.
My specific travel includes roughly 28% City & 72% Highway.
When first purchased CPO @ 35,xxx miles this vehicle was getting around 30-33 MPG for the same route I travel to this day. I have not had any issues with this vehicle until its first service appointment. I am now showing 21 MPG displayed on the Information Center however doing the math of how many miles were driven with how many gallons were pumped and I consistently show 19 MPG. I am by no means a lead-foot and I know that certain conditions can affect the MPG I receive but not that drastically right?

Work that has been done to the vehicle since purchase:
Engine Intake Manifold @ 42k
Injector for Cylinder 3 @ 42k
Software Update to resolve a false O2 Sensor Code @ 45k
Radio Software Update

After the Engine Intake Manifold and the Injector for Cylinder 3 were replaced is when I started seeing the issue with my fuel economy as well as a handful of other issues.
I am fully aware that Winter Fuel Blends can sometimes have a negative effect on the MPG, but I can't accept the dealership telling me that its acceptable to go down to 11-14 MPG due to a winter fuel blend. With no check engine lights or any DTC being pulled they refuse to even look at it and my Warranties are running out very very soon. Any help/advice on how to track down the issue would be fantastic!

It may also be worthy to note that even though I have no DTC / MIL showing I have been experiencing a very rough idle from cold start and a massive vibration/bass coming from the engine bay at certain times during idle and gets progressively louder until I hit 2,200 RPM's.

Hopefully this is being posted in the right area and if not can someone direct me to the proper place to post or if the post has been made already direct me towards that. I have searched and cannot find much info.

 

[campb292]

Welcome! You definitely posted in the right section. Thank you also for providing such detailed info!

When first purchased CPO @ 35,xxx miles this vehicle was getting around 30-33 MPG for the same route I travel to this day.

That is right where it should be for your usage.

I am now showing 21 MPG displayed on the Information Center however doing the math of how many miles were driven with how many gallons were pumped and I consistently show 19 MPG.

Assuming this is over at least a tank or two/at least 500 miles, this is not right. Mileage that low is not winter blends.

After the Engine Intake Manifold and the Injector for Cylinder 3 were replaced is when I started seeing the issue with my fuel economy as well as a handful of other issues.

It is going to be this. Either a mis-diagnosis or poor work. Too big of a coincidence. Did you have codes or warnings that led to these replacements? Have you spoken with your service manager sharing these concerns?

 

[nbrown0529]

It is going to be this. Either a mis-diagnosis or poor work. Too big of a coincidence. Did you have codes or warnings that led to these replacements? Have you spoken with your service manager sharing these concerns? Funny you mention that. I have spoken to the service manager about why it had to be replaced. After the Manifold was swapped out they called me and told me my car was ready to be picked up and upon arrival they drove the car up to me and it was popping and running rough with a CEL. They decided to keep the vehicle and told me that the injector had went bad and was causing a bad misfire on the vehicle ( I have documentation at home ) However it seems funny that it went bad after the manifold was replaced. I was then charged roughly $1200 parts and labor because this wasn't covered under the Powertrain Warranty. My service manager refuses to look at my vehicle with any of the concerns I have had and continues to ramble on about needing a DTC and or a CEL and that the Winter Fuel blends are the issue. I feel there is more going on behind the scenes even if there aren't any DTC's. Assuming this is over at least a tank or two/at least 500 miles, this is not right. Mileage that low is not winter blends. The 19 MPG I get is under a full tank (i.e 13 Gal Tank)

 

[campb292]

How many miles has it been since the replacements? Besides the low mpg, any rough idle, unusual noises, oil level and condition look good? Coolant staying level in the tank?

 

[nbrown0529]

How many miles has it been since the replacements? Besides the low mpg, any rough idle, unusual noises, oil level and condition look good? Coolant staying level in the tank?

It has been roughly 13k miles. I am currently at 55,xxx and service was performed around 42,xxx or 45,xxx. I have a massive vibration coming from the engine bay which disappears around 2,200 RPMS, acceleration is very hesitant from a stop and go and almost feels as if there is no real power until it hits 4k RPMS. Coolant level and oil consumption is normal. No fuel in the oil or anything out of the ordinary.

It may also be worthy to note that even though I have no DTC / MIL showing I have been experiencing a very rough idle from cold start and a massive vibration/bass coming from the engine bay at certain times during idle and gets progressively louder until I hit 2,200 RPM's.

 

[campb292]

I'd want to do a compression and leakdown test. If you have no codes they probably won't do this for free. You might need to pay and may want to have independent shop do it. The test might reveal nothing abnormal but you can rule out some issues from it. If it fails, hopefully your cpo warranty is in effect and you can address the problem.

The vibration at 2200 rpm is interesting. Is that definitely a noise from the engine and not coming from your speakers as a loud bass drone/rumble?

Even more interesting is the lack of power until 4000 rpm. That is a behavior reported by owners of the 2018 1.5 and is attributed to knock sensor problems. Basically, the sensors detect knock and retard the timing accordingly. This will give horrid mpg like you have and lack of power. The problem here is you don't have a 2018 so the software anomoly doesn't exist; it might actually be detecting knock and pulling timing. A tech needs to check with a scan tool to see if this is happening on your car.

 

[nbrown0529]

I'd want to do a compression and leakdown test. If you have no codes they probably won't do this for free. You might need to pay and may want to have independent shop do it. The test might reveal nothing abnormal but you can rule out some issues from it. If it fails, hopefully your cpo warranty is in effect and you can address the problem.

The vibration at 2200 rpm is interesting. Is that definitely a noise from the engine and not coming from your speakers as a loud bass drone/rumble?

I appreciate the information and I will begin looking into that compression test. I’d rather do something instead of waiting for more problems to arise. As far as the vibration is concerned, I have tested with radio on and off volume all the way down and I still get the vibration.

Even more interesting is the lack of power until 4000 rpm. That is a behavior reported by owners of the 2018 1.5 and is attributed to knock sensor problems. Basically, the sensors detect knock and retard the timing accordingly. This will give horrid mpg like you have and lack of power. The problem here is you don't have a 2018 so the software anomoly doesn't exist; it might actually be detecting knock and pulling timing. A tech needs to check with a scan tool to see if this is happening on your car.

What are the possibilities of having a tapping sound that can be heard with the engine running due to this? I know my car doesn’t really fall under this issue but can it cause a sound such as a lifter tapping?

 

[campb292]

I hesitate to suggest much about noises. What is most important are noises you haven't heard before. Recording noises and sharing sometimes help but tech diagnosis is preferred. Noises in general are tough on these. Outside the car all sorts of soft ticks and tings can be heard. Same noises on any direct injection vvt engine. What you shouldn't hear is any of it inside the car. You should hear a smooth sound. Knock sensors are calibrated to specific vibrations and frequencies and won't be thrown by common noises. I think noise and vibration... I honestly haven't read much about them. Hopefully others have thoughts.

 

[cp-the-nerd]

I don't know what sort of recourse you have, but that "repair work" really did a number on your car. The problem with these situations is it's nearly impossible for us to speculate what they did wrong over the internet, but they totally screwed you over when they killed your fuel economy and then refused to work with your concerns.

It's an awful sign of incompetence when they tell you the car is ready, but bring it out misfiring and throwing codes. Never go back there again. I don't know if it's a practical solution for you, but I would contact another repair shop (GM or otherwise reputable) and explain your situation with the intake manifold repair and the "sudden injector failure" as well as your fuel economy woes. You'll be paying out more money, but someone might be able to sort you out.

You could always trade the car in for something else.

 

[repairman54]

Is this a Chevy dealer, if so get on the horn to GM corporate and explain what they did. Dealer is a franchise and corporate doesn't want poor dealers chasing away their customers to other brands.

 

[ggogan]

I have had good experience with two Malibus but only on 2 yr leases so the mileage was under 25 K. I finally purchased the third one- a 2017 lease turn in. So far no major problems
but I have had it in for service a few times for bad bearings / hubs which were replaced under warranty. However while there they tried to sell me a big service package
for around $650 - items not under warranty. It happened a few times. I have wondered if GM is telling their managers to look for billable items to help offset the cost of covering
warranty items. I hate to imagine that but do have to wonder about it and stories like this add to that.

 

[DrivenDaily]

I have had good experience with two Malibus but only on 2 yr leases so the mileage was under 25 K. I finally purchased the third one- a 2017 lease turn in. So far no major problems
but I have had it in for service a few times for bad bearings / hubs which were replaced under warranty. However while there they tried to sell me a big service package
for around $650 - items not under warranty. It happened a few times. I have wondered if GM is telling their managers to look for billable items to help offset the cost of covering
warranty items. I hate to imagine that but do have to wonder about it and stories like this add to that.

That is standard business in any dealership. I worked in a Ford dealership for 5 years and there were always bonuses to be had for selling services, including ones that fell during the warranty period and weren't actually needed.

 

[repairman54]

2x standard service up selling in any service business. Value added services to enhance the customers experience and provide the most satisfaction and trouble free operation. That is the pep talk / mantra that is given to every service dept. no matter what industry.

 

[campb292]

That is standard business in any dealership. I worked in a Ford dealership for 5 years and there were always bonuses to be had for selling services, including ones that fell during the warranty period and weren't actually needed.

I can attest to this being a common dealership behavior. When my Subaru goes in each time they tell me about the free 27-point inspection and then pull out the sheet and try selling me a $39.95 172-point inspection upgrade. It includes things like "verify hood release function" and "verify side view mirror rotation". They also do the typical $49.95 cabin air filters and $29.95 wiper refills. I don't really see a problem with it if they actually do it and for some people figuring out what filter, where it goes, and actually doing it isn't worth their 50 bucks. I personally enjoy it and know it gets done right.

However, it certainly isn't something every industry engages in. I just had GE service out to repair a squeaking dryer and the guy just repaired the dryer under warranty and left. He didn't try selling me $84 performance enhancing door hinge lubricant or a knob shine for $49.95.

 

[DrivenDaily]

Well, he was out of dryer alert chime fluid or he'd've sold ya some.

 

[repairman54]

He didn't try to sell you a extended warranty ??? That is unless you have one already or he was not actually GE factory but a authorized servicer as independents do not deal with that non sense.
Every factory service puts the techs under the gun to up sell but end of the month so he may have met his quota.