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Discussion Starter #1
Over the past few months my 2010 malibue 2.4L (120k miles) has had the check engine light come on randomly. I would reset it as it was running fine and it would go away for anywhere from a day to a few weeks. I have a state inspection coming up so I am finally getting to the bottom of this issue. so far I have tried.

1. new spark plugs
2. swapped coils.
3. swapped injectors.
4. applied dielectric grease to the injector.
5. cleaned the engine with seafoam.
6. fresh oil change
7. cleaned MAF sensor
8. I did a compression test and cylinder 1 was a little low, but maybe only 12% off from the other cylinders (not 100% sure if did correctly, I want to try again)

The misfire seems to happen at random intervals and I have noticed it only seems to click the CEL at idle and usually trips my traction control service light. The car starts fine, has a normal idle for a car with that man miles, and drives/accelerates normally.

A few things to note. There is an aftermarket sub hooked up to the battery(new battery 6 months ago) and plugged into the MAF sensor fuse slot (i didnt not install, came with the car)

Now I know it could be piston or engine issue, but I am trying to rule out any other issue before I drop that kind of cash. I head heard of the wiring harness going bad, I did a visual inspection and the wires were worn, but no visible breaks. I checked the injectors and it was getting power, but i would assume its getting power most of the time if I am only having an issue every 70-150miles.

Another thing to note, I am having issues getting my EVAP OBD reading to ready up. All my other sensors are ready, but I can't get the EVAP sensor to kick on so I can get my test done before the CEL clicks on again.
 

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Get the sub feed out of the MAF slot first.
It could be creating electrical noise in the CAN system. CAN is very sensitive to anything aftermarket, that's why they even sell CAN safe LED bulbs.
I would disconnect anything not factory in the car and go from there.
Engine coil and injector harness can be a intermittent issue also, those wires are so small.
301 is cylinder one so focus there if it still happens after getting aftermarket stuff out of the data stream.
 

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Discussion Starter #3
Get the sub feed out of the MAF slot first.
It could be creating electrical noise in the CAN system. CAN is very sensitive to anything aftermarket, that's why they even sell CAN safe LED bulbs.
I would disconnect anything not factory in the car and go from there.
Engine coil and injector harness can be a intermittent issue also, those wires are so small.
301 is cylinder one so focus there if it still happens after getting aftermarket stuff out of the data stream.
I will remove that wire, how can i find what fuse does in the slot?
I am going to a salvage yard to see if there are any good looking harnesses I can steal, i have heard of the wire issue. I have also heard of issues with the ignition control module causing problems,but I have no idea how to even test for that.


Do you have an idea why I only seem to get the misfire issue at 80+ miles after reset, and at idle?
 

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Intermittent problems are the hardest to fix.
Check all your grounds to the engine also. Fuse box cover will tell you what size fuse if any goes where. Sometimes someone will just jam a wire into the fuse box to pick up a switched hot which sounds like what you have instead of using a add a line adapter on a circuit
Usually a bad module will not go 80 miles before it acts up, sounds more like a poor connection some where. .
 

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Discussion Starter #5
Intermittent problems are the hardest to fix.
Check all your grounds to the engine also. Fuse box cover will tell you what size fuse if any goes where. Sometimes someone will just jam a wire into the fuse box to pick up a switched hot which sounds like what you have instead of using a add a line adapter on a circuit
Usually a bad module will not go 80 miles before it acts up, sounds more like a poor connection some where. .
How do I check the grounds?
 

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Make sure battery connections are tight and clean. Zero corrosion on cables. There are black wires/cables that connect to the body and frame of the car from the engine and battery. The black ones connecting to the body of car are the grounds. Grounds must be clean and tight.
It's not simple to undo what a previous owner may have screwed up.
 

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Discussion Starter #7
Make sure battery connections are tight and clean. Zero corrosion on cables. There are black wires/cables that connect to the body and frame of the car from the engine and battery. The black ones connecting to the body of car are the grounds. Grounds must be clean and tight.
It's not simple to undo what a previous owner may have screwed up.
I went to a salvage yard yesterday and got a new injector harness (well a newer and less brittle one), a new gas cap, and I got a a different PCM ( i don't know if if this will help anything, I remember reading there was an issue with this on some cars, not sure if i can just swap them or not). This weekened I am going to remove the aftermarket subwoofer and undo all the grounds I can find to scrub them and re-tighten them.
 

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Discussion Starter #8
I wanted to follow up. I swapped out the injector wiring harness and it seems to have fixed the problem. I am 200+ miles and haven't had my CEL come on. The car runs great and passed my inspection.
 
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