[AcidiC]

Hey guys,

I'm a long time lurker here since I've got the Cobalt in August 2012, and I have been enjoying the site immensely. You all have beautiful cars that I would love to try match the looks one day. Sorry that I haven't involved myself in this community, but I don't bring a lot of knowledge.

Anyways guys, here are my issues that I've been having.

2010 Cobalt LS 2.2

1. My MPG is down by a lot. I'm Canadian and I don't use the MPG system, but I'm averaging about 10.2-10.4 Litres per / 100KM (this number will drop on the highway) and I only got 417 KM's on my last full tank. When I first got my car it was amazing on gas. Roughly about 530-540 KM's depending on my driving.

What could possibly cause me to lose over a 100 KM's to a tank?

2. Additionally, since I've discovered this issue, I have noticed some other problems. Once in awhile the start sounds a little rough for a split second. Like the grinding of chains for a brief, brief moment. Doesn't happen all the time.

3. When warming up the car and throttling minor RPM in Park, the car will return to idle, but RPM throttles weirdly in doing so, and once in awhile, for a split second, feels like it could actually stall, but stabilizes. Once the car hits the road it feels fine. It doesn't feel like a major issue, but it doesn't feel right.

4. Once in awhile when driving, the RPM will just die for a split moment, then rev right back up. Such as when I'm stopped at a Red light and it turns green. Once again this doesnt happen often, but its a weird sudden loss in power. I'll have to double tap the gas at this point.

So I'm wondering what this could be? I'll try and give you a few answers as to what I've done with the car as well as what others have said it could be.

I've been running premium gas through the vehicle in the last 3 weeks as well to do whatever I can to help the engine. I heard this will burn hotter, and help clean. So why not?

I got the car at 19,000 km August 2012. Its now at 54000 KMs. Its been through oil changes every 4k-5k KM's and on my most recent change I flushed the system.

Friend said it could be air filter (which I havent changed), fuel filter, winter gas, O2 sensors, spark plugs need cleaning etc.

But I'm on a low budget and have no idea where to start? Air Filter?


EDIT: Forgot to mention bumper to bumper has expired, but I have power train warranty until December 2015. And I'm fairly certain powertrain is not going to help me here.

Thanks in advance to anyone that can help.

Cheers,

 

[Coby7]

Try cleaning your throttle body first, this cost nothing. Just make sure you don't leave key in ignition.

 

[AcidiC]

I've never even heard of that before. Gosh, something new every time. This looks relatively easy though. Won't hurt to try it out, but I'm not confident working under the hood.

Seems like this could be the problem, or part of it. Thanks for the feedback.

 

[Coby7]

If you don't trust yourself bring to a friendly mechanic, I can't see them charging too much for this simple job. I think there's a DIY on here.

---------- Post added at 06:06 PM ---------- Previous post was at 05:59 PM ----------

Throttle Body Cleaning
Remove the air cleaner outlet duct. Refer to Air Cleaner Outlet Resonator Replacement .
Inspect the throttle body bore and the throttle valve plate for deposits. You must open the throttle valve in order to inspect all of the surfaces.
Notice: Do not subject a throttle body assembly which contains the following components to an immersion cleaner or a strong solvent:

• Throttle position (TP) sensor

• Idle air control (IAC) valve

• Sealed throttle shaft bearings

The cleaners will damage the electric components or sensors.

The cleaners will damage some of these components that contain seals or O-rings.


Solvents can wash away or break down the grease used on non-serviceable throttle shaft bearings.


Never use a wire brush or scraper to clean the throttle body. A wire brush or sharp tools may damage the throttle body components.


Do not use a cleaner that contains methyl ethyl ketone. This extremely strong solvent may damage components and is not necessary for this type of cleaning.

Clean the throttle body bore and the throttle valve plate using a clean shop towel with Top Engine Cleaner, GM P/N 12346535, (Canadian P/N 992872) or Saturn P/N 21007129 or an equivalent product.
If the deposits are excessive, remove and disassemble the throttle body for cleaning. Refer to Throttle Body Assembly Replacement .
After disassembly, clean the throttle body using a parts cleaning brush. DO NOT immerse the throttle body in any cleaning solvent.
If you removed and disassembled the throttle body for cleaning, assemble and install the throttle body. Refer to Throttle Body Assembly Replacement .
Install the air cleaner outlet duct. Refer to Air Cleaner Outlet Resonator Replacement .
Air Cleaner Outlet Resonator Replacement
Removal Procedure


Disconnect the intake air temperature (IAT) sensor harness connector.
Loosen the air cleaner assembly fresh air duct to resonator clamp.



Remove the push-pin fastener from the air outlet resonator/duct assembly to support bracket.
Loosen the resonator to throttle body clamp.
Disconnect the air cleaner assembly fresh air duct from the resonator.
Remove the air outlet resonator from the throttle body.
Installation Procedure




Install the air outlet resonator to the throttle body.
Connect the fresh air duct to the air outlet resonator.
Notice: Refer to Fastener Notice in the Preface section.

Tighten the air outlet resonator to throttle body clamp.
Tighten
Tighten the clamp to 5 N·m (44 lb in).

Align the air outlet resonator to the bracket and install the push-pin fastener.



Connect the air cleaner assembly fresh air duct to the air outlet resonator.
Tighten
Tighten the clamp to 5 N·m (44 lb in).

Connect the IAT sensor harness connector.

Throttle Body Assembly Replacement
Removal Procedure
Notice: Do not use solvent of any type when cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as damage to the gasket surfaces and throttle body assembly may result.

Use care in cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as sharp tools may damage the gasket surfaces.


Notice: Do not use any solvent that contains Methyl Ethyl Ketone (MEK). This solvent may damage fuel system components.

Remove the air cleaner resonator. Refer to Air Cleaner Outlet Resonator Replacement .



Disconnect the idle air control (IAC) valve harness connector (1).
Disconnect the throttle position (TP) sensor harness connector (2).
Disconnect the vacuum hoses at the throttle body.



Remove the throttle body attaching bolts (1).
Remove the throttle body (4) from the intake manifold.
Installation Procedure




Inspect the throttle body gasket (3) and replace if necessary.
Install the throttle body (4) to the intake manifold.
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

Install the throttle body attaching bolts (1).
Tighten
Tighten the throttle body attaching bolts to 10 N·m (89 lb in).

Connect the vacuum hoses to the throttle body.



Connect the TP sensor harness connector (2).
Connect the IAC valve harness connector (1).
Install the air cleaner resonator. Refer to Air Cleaner Outlet Resonator Replacement .
Test the accelerator movement by depressing the pedal to the floor and releasing the pedal.

 

[keegs]

If I can do it anyone can.

Driving style, whether you're driving local or highway, traffic congestion, temperature ....have an impact on fuel economy.

I saw great numbers for about the first 40k miles. Summer months, when school traffic declined and average outside temp increased I was seeing 41mpg US. Last summer though I was lucky to see 39. Not sure what's caused the decline. I replaced the air filter and did the TB cleaning and it didn't seem to help....getting 36 mpg right now.

 

[ChevyCustSvc]

Hello AcidiC,

I am sorry to hear you are having this concern. If you decide to have your Chevrolet dealership look into this for you, please reach out to GM of Canada as well. They can be reached at 800-263-3777.

Erica Tiffany
Chevrolet Customer Care

 

[tred07]

sounds like some of the same symptoms i had.if cleaning does not help replace!