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Discussion Starter · #1 ·
My name is Dave and my fiancé owns a 2012 Chevy Cruz. She has had it for 10 months and has been nothing but problems for the last six. I need some insight on code p0303. I have a misfire on cylinder three and having trouble finding out what’s causing it. I just change the spark plugs so it shouldn’t be that. I’ve tried adding fuel injector/system cleaner and it helps for a day or so but then goes back to running rough. My girl Stepdad said to try spraying carb cleaner on the intake while it’s running to see if it makes it run smoother because he thought there was a crack or leak in the intake but that didn’t work. I’m thinking it might just be a bad injector sense the fuel cleaner seems to work for a day or so. Should I try a new injectors or does anyone have any insight?
 

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Did you make sure the little spring inside the coil boot for that cylinder was down, and not still shoved up into the boot? It needs to be touching the spark plug. Common missed item....

Sent from my SM-G986U using Tapatalk
 
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Discussion Starter · #3 ·
No I didn’t, I don’t know a ton about cars but I’m pretty mechanically inclined so I will look into it. Don’t you think it would have something to do with the fuel system though since it runs smooth when I add fuel system cleaner?
 

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p0303 means cylinder 3 is having a misfire. I would check the spark plug gap for that cylinder to make sure it's right, then check the springs on the coil pack. If neither of those is the issue, I would test your coil pack and then your injector.

If it's happening on cylinder 3 those are your first big steps.
 

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p0303 means cylinder 3 is having a misfire. I would check the spark plug gap for that cylinder to make sure it's right, then check the springs on the coil pack. If neither of those is the issue, I would test your coil pack and then your injector.

If it's happening on cylinder 3 those are your first big steps.
@dsmith There is no known DIY test on the coil assembly. There are multiple mosfet transistors wired onto the circuit board within the coil assembly.

you didn’t mention if you have the 1.8l or the 1.4l, chances are good that you just have a bad coil as these tend to be a failure point.

1.4l are known to have piston issues ( hopefully that’s not you )

easiest way I know is to pick up a coil assembly and plug a new one in. If it doesn’t fix your issue just return it for a refund.
 

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Discussion Starter · #6 ·
Well I just replaced all the injectors with AC Delco new ones and it seems to be running smoother. I’m about to head home and plug the scanner back in and see what it says.
 

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Discussion Starter · #7 ·
This is a few hours after I put new injectors in, and it was running smoothly at first and now it started to run a little bit rough again. And I did check the spring in the coil boot like you told me to and all the springs were fine. I don’t know what to do now.
 

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Discussion Starter · #8 ·
And I just replace the spark plugs two months ago, the next step I would think would be to buy a coil pack. What’s the thing that gets me is that why does it run smoother when I put fuel cleaner in it, I would just think that it would have to do something with the fuel system with the injectors that I just bought didn’t seem to help that much so what now
 

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2014 LT program car, Pull Me Over Red, 1.4T Auto
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My name is Dave and my fiancé owns a 2012 Chevy Cruz. She has had it for 10 months and has been nothing but problems for the last six. I need some insight on code p0303. I have a misfire on cylinder three and having trouble finding out what’s causing it. I just change the spark plugs so it shouldn’t be that. I’ve tried adding fuel injector/system cleaner and it helps for a day or so but then goes back to running rough. My girl Stepdad said to try spraying carb cleaner on the intake while it’s running to see if it makes it run smoother because he thought there was a crack or leak in the intake but that didn’t work. I’m thinking it might just be a bad injector sense the fuel cleaner seems to work for a day or so. Should I try a new injectors or does anyone have any insight?
Welcome Aboard!(y)

A code P0303 may mean that one or more of the following has happened:
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer
Read more at: OBD-II Trouble Code: P0303 Cylinder 3 Three Misfire Detected


Don't forget to introduce yourself and your Cruze here.
This is a cut and paste from a similar thread so it may be out of order for you:

#16-NA-015: Engine Stall or Stumble - Replace Coil Connector - (Jan 21, 2016)

https://static.nhtsa.gov/odi/tsbs/2016/MC-10112283-9999.pdf



Pull the ECM connector and look for corrosion. If you have any read this:
Burning up Coil pack
Blown Coil, Misfire problem SOLVED!!!
Coil blow out

or

Pull off the spark plugs boot and inspect the spring. It should have a resistor pellet integrated into. Measure the resistance of the spring from one end, to the end of the resistor pellet(looks like a tiny fuse or capsule usually). You should have somewhere between 800-1200ohms resistance. If you just have a plain spring, or if the resistance is below 800 or so, that's why you're blowing out coils. (Courtesy of Ma v e n)


And lastly:


https://static.nhtsa.gov/odi/tsbs/2016/MC-10112283-9999.pdf

Tips to ensure no misfires occur:

Remove the coil pack. If the boots are stuck on, use a small screwdriver or pick with some dielectric grease on it to go around the outside of the boot and then possibly the inside of the boot to help aid in removal.

Remember to (p)re-gap your plugs to .028, (0.24 if tuned)

Set gap with the black portion of this tool.



To increase the gap size bend the ground strap up to the desired height. DO NOT LET THE GAPPING TOOL TOUCH THE IRIDIUM CENTER ELECTRODE OR PORCELAIN.

Measure the gap with feeler gauges.



Throw this away.





Torque to 18 ft-lbs with no anti-seize on the threads of a stock type plug.

Ensure the boots have no rips/tears or holes in them, lightly coat them with dielectric/silicone grease and make sure the resister springs are clean and not caught up in the boots when you install them.

If the plugs look bad, consider these:

-BKR8EIX-2668 (iridium plugs), ~$25, expect ~10-15k regaps on these, ~40-50k overall life.
-BKR7E-4644 (nickel/copper plugs), ~$8, expect 15-25K out of these plugs, with a regap or two required at 5-8k intervals on stock tune.
-FR7BHX-S (Ruthenium HX plugs)

Read Hesitation Gone! for more info on the plugs.


A good replacement coil is the MSD Blaster OEM Replacement Coilpack 8236

How-To: Remove and Replace the Coil Pack and Spark Plugs.

While you are in there, if you have a cheap endoscope, look at the pistons. This can also tell you many things.

Cheap compression tester
 

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Discussion Starter · #10 ·
So quick ?. Since the coil pack is a pack and not individual coils , would the whole pack go bad instead of just the one on cylinder 3, ( where my misfire is). My girls stepdad is saying that coil packs will normally just fail altogether, so it’s probably not the coil that’s the problem. He’s saying most likely it’s the intake manifold . That it has a leak somewhere, being the manifold itself or a gasket. I’m hoping that isn’t the case cuz I’ve watched a couple videos on replacing the intake and it looks pretty intricate and I don’t have a ton of experience working on cars. I replaced the injectors and I did that relatively easy but replacing an intake looks way harder but I really don’t wanna foot the bill on having a shop do it.
 

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So quick ?. Since the coil pack is a pack and not individual coils , would the whole pack go bad instead of just the one on cylinder 3, ( where my misfire is). My girls stepdad is saying that coil packs will normally just fail altogether, so it’s probably not the coil that’s the problem. He’s saying most likely it’s the intake manifold . That it has a leak somewhere, being the manifold itself or a gasket. I’m hoping that isn’t the case cuz I’ve watched a couple videos on replacing the intake and it looks pretty intricate and I don’t have a ton of experience working on cars. I replaced the injectors and I did that relatively easy but replacing an intake looks way harder but I really don’t wanna foot the bill on having a shop do it.
There are reasons for just one coil in the pack to read bad. It could be the cleanliness of the springs and/or the pellet, the boots, the plugs etc. Did you read through all that I posted? The answer to your questions are very likely to be answered in those posts.
 
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