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Discussion Starter · #1 ·
So I have a 2012 cruze auto and 2 days ago coming home I was giving it some gas while manually locked in 6th gear on the highway and it all of a sudden started misfiring really really badly and felt like a multi-cylinder misfire. Now it will misfire under anything but the absolute lightest throttle and gets worse with load and will occur at idle.I've been taking it very easy since then but coming home this morning after a downshift to get up a hill the torque converter wouldn't lock in any gear for about 2 miles but then suddenly locked and went back to normal the rest of the drive home. Also there is a small jump in timing by a few degrees every time it misfires at idle looking at my scanner.Can the trans issue in any way be caused by the misfire?What should I look for to narrow down the cause of the misfire?Thanks.
 

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So I have a 2012 cruze auto and 2 days ago coming home I was giving it some gas while manually locked in 6th gear on the highway and it all of a sudden started misfiring really really badly and felt like a multi-cylinder misfire. Now it will misfire under anything but the absolute lightest throttle and gets worse with load and will occur at idle.I've been taking it very easy since then but coming home this morning after a downshift to get up a hill the torque converter wouldn't lock in any gear for about 2 miles but then suddenly locked and went back to normal the rest of the drive home. Also there is a small jump in timing by a few degrees every time it misfires at idle looking at my scanner.Can the trans issue in any way be caused by the misfire?What should I look for to narrow down the cause of the misfire?Thanks.
yes, the trans is fine. I would look into your coil pack, the 7 pin harness connected to it, and spark plugs. pull the boots off the coil and check for corrosion on the resistors...they are inside the boots touching the bottom of the coil pack.
 

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I'd replace the coil pack as well.

Don't continue to drive the car in this condition; you will destroy the expensive catalytic converters.
 

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Discussion Starter · #4 · (Edited)
Thank you.Ive now narrowed the issue down to cylinder 4 looking at the misfire counter(forgot how to get the counter up until now as I haven't used my scanner in a while).I suppose the pcm could tell the converter not to lock because of the shock placed on other components when there's a high amount of misfires and the converters locked,but this is purely speculation on my part as I'm unsure if GM has programmed this car to do that.Now I'll check the coil pack and the spark plug on cylinder 4 and see what it looks like.
 

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Thank you.Ive now narrowed the issue down to cylinder 4 looking at the misfire counter(forgot how to get the counter up until now as I haven't used my scanner in a while).I suppose the pcm could tell the converter not to lock because of the shock placed on other components when there's a high amount of misfires and the converters locked,but this is purely speculation on my part as I'm unsure if GM has programmed this car to do that.
Ah crap, a cyl 4 one again...

Ok, yes, inspect the coil pack - you will probably find it cracked/failed, but also check the ECM connectors (next to the battery) for corrosion/burnt pins. It has been quite common lately.
 

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Discussion Starter · #6 ·
Hmmm.I checked the plug for wear and it looks fine though it may need to be re-gapped.The plug threads however were completely covered in rust and there was some type of white\green corrosion on the plug terminal even though I cleaned the same type of corrosion off of the terminal yesterday thinking that might have been the issue.The spring on the coil pack for cyl 4 also had some corrosion on it however it otherwise looks good visually as do the connectors.
 

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Hmmm.I checked the plug for wear and it looks fine though it may need to be re-gapped.The plug threads however were completely covered in rust and there was some type of white\green corrosion on the plug terminal even though I cleaned the same type of corrosion off of the terminal yesterday thinking that might have been the issue.The spring on the coil pack for cyl 4 also had some corrosion on it however it otherwise looks good visually as do the connectors.
did you check the resistor that's on top of the spring?? did you happen to shine a light into the cylinder and see what the top of the piston looks like? see pics for reference.
 

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Discussion Starter · #8 ·
292634
Here is my spring and resistor which has some corrosion as well.I looked at the top of the piston with my borescope and other than some carbon buildup on one portion it is spotless.
 

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View attachment 292634 Here is my spring and resistor which has some corrosion as well.I looked at the top of the piston with my borescope and other than some carbon buildup on one portion it is spotless.
Some corrosion, good lord that thing looks like it's been hanging out beside the ocean salt water.
 

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Discussion Starter · #11 ·
Thank you Shroomie I'll replace the coil pack.But out of curiosity what would've caused it to become so corroded in the first place?
 

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Thank you Shroomie I'll replace the coil pack.But out of curiosity what would've caused it to become so corroded in the first place?
heat cycles and humidity. those boots don't always seal 100% they do a relatively good job, but we have seen a lot of this here on the forums. you may notice only 1 or 2 look like that and the others are fine.
 

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Thank you Shroomie I'll replace the coil pack.But out of curiosity what would've caused it to become so corroded in the first place?
put a light coating of dielectric grease around the outside of the boots. don't put any inside the boots or on the plugs. it's an insulator.
 

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Thank you Shroomie I'll replace the coil pack.But out of curiosity what would've caused it to become so corroded in the first place?
I opened my hood after driving in the rain one time...noticed the coil pack was wet on the passenger side.. infact, a lot of drops on that side of the car. the seal on the hood that goes over the headlight was not making contact... there was a gap. the other side was good. make sure the seals around the headlights are good.
 
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