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Discussion Starter · #1 ·
Alright guys, I developed a misfire almost home from Lordstown. It only registers the misfire at idle, but below 2k RPMs in 4-6th gear it'll miss as well.

It pulls WOT perfectly fine, and just as powerful as normal.

No drivability problems besides the below 2k miss in 4-6th gear and at idle.

It's only cylinder 1. Attached is a picture of the plug I pulled out of cylinder one.

I swapped cylinder 1-2 plugs and the coils from 1 and 4. The misfire remained on cylinder 1.

My mechanic friend has only seen it once before, years and years ago, but it was an injector issue.

Anybody else want to brainstorm?



 

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If you confirmed spark, it either has to be fuel or air. Easy thing to do first is put a compression gauge on it to rule out a burnt valve other mechanical issue. Once that is done go from there.
 

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Discussion Starter · #3 ·
If you confirmed spark, it either has to be fuel or air. Easy thing to do first is put a compression gauge on it to rule out a burnt valve other mechanical issue. Once that is done go from there.
Question; if it was a burnt valve or something, wouldn't I have an issue with a WOT pull from 0 mph in first to 80 in third?
 

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Take a look at the spring coil. We've seen corrosion on the coils in the past. Corrosion will cause the car to misfire at low RPM while allowing the more frequent electrical charges at higher RPM to get through to the plug.
 

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Discussion Starter · #5 ·
Take a look at the spring coil. We've seen corrosion on the coils in the past. Corrosion will cause the car to misfire at low RPM while allowing the more frequent electrical charges at higher RPM to get through to the plug.
You're talking about the spring inside the boot?
 

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I'm not familiar with the new 1.4.......is it Direct Injection?
If it is, this most likely will be a injector issue......I'm thinking high resistance but a possibility of the injector being slightly obstructed at the pintle.

When at higher engine speeds (and load) the injector opens further, possibly (in this case) enough to overcome the lean condition (misfire).

Best wag I can come up with from a keyboard.

Rob
 

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Discussion Starter · #7 ·
I'm not familiar with the new 1.4.......is it Direct Injection?
If it is, this most likely will be a injector issue......I'm thinking high resistance but a possibility of the injector being slightly obstructed at the pintle.

When at higher engine speeds (and load) the injector opens further, possibly (in this case) enough to overcome the lean condition (misfire).

Best wag I can come up with from a keyboard.

Rob
It is direct injected.
 

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It's under warranty and you work at a Chevy dealer, why not let them fix it rather than guessing what the problem is?
 

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Beyond the coil itself being bad, I can think of two possibilities - one that they're known for:

1) Valve isn't closing completely due to carbon build-up. Compression won't be zero, but it will be slightly low. Shouldn't yet be an issue with an engine with so few miles on it, and that would be terrible news for other LE2 owners.
2) Cracked piston. Two have had it happen on LE2's already on cyl #1 (and it happens all the time with LUJ/LUV engines), but I think they both ran 87 oct. And then there's the issues with the 1.5 which is almost mechanically identical to the 1.4.

I think my first diagnostic tool would be a simple compression test. If that checks out ok and is within the range of all of the other cylinders, then you could begin by switching coil packs between cylinders to see if that makes a difference, or looking into an injector issue, which would be a new one to me.
 

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Discussion Starter · #10 ·
Beyond the coil itself being bad, I can think of two possibilities - one that they're known for:

1) Valve isn't closing completely due to carbon build-up. Compression won't be zero, but it will be slightly low. Shouldn't yet be an issue with an engine with so few miles on it, and that would be terrible news for other LE2 owners.
2) Cracked piston. Two have had it happen on LE2's already on cyl #1 (and it happens all the time with LUJ/LUV engines), but I think they both ran 87 oct. And then there's the issues with the 1.5 which is almost mechanically identical to the 1.4.

I think my first diagnostic tool would be a simple compression test. If that checks out ok and is within the range of all of the other cylinders, then you could begin by switching coil packs between cylinders to see if that makes a difference, or looking into an injector issue, which would be a new one to me.
I already swapped coils, misfire stayed on cylinder one.

Misfire doesn't happen on a WOT pull. It pulls hard like normal all the way to redline.

It's certainly a confusing one for me.
 

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My best guess is fuel at this point or something weird with ignition

Bad ground that fixes itself at wot because it just powers through or it jimmies itself into a better position? Long shot but maybe

I'd pretty much say fuel at this point try moving injectors around?


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Discussion Starter · #12 ·
My best guess is fuel at this point or something weird with ignition

Bad ground that fixes itself at wot because it just powers through or it jimmies itself into a better position? Long shot but maybe

I'd pretty much say fuel at this point try moving injectors around?


Sent from my iPhone using Tapatalk
The problem with moving injectors that day was that I didn't want to risk pulling an injector and not having a crush washer to replace.
 

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Best bet is injector issue, I doubt it would be a ground issue because then the misfire would be sporadic throughout the rpm band.


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Discussion Starter · #14 ·
I've had a couple people suggest cracked piston. I have it scheduled to go in to service on Thursday, because that's the first day a loaner vehicle will be available to me. I did mention my concerns and my issues, so either it'll be fine until Thursday and then be fine, or it'll explode and I'll not worry because they told me I could wait until Thursday.
 

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I'm starting to sound like a cranky old man, eliminate the easy stuff first. Before messing with injectors, coil packs etc or guessing about other parts, pull a compression test. It is an easy diagnostic to complete. I will take less than an hour to complete. Once you know things are mechanically sound start going after fuel injectors, coil packs, or other electrical gremlins. If you have lower compression on #1, that will be the root of your misfire.

My sons S10 with a 4.3 kept throwing a P300. A new distributor cured the P30, but promptly got a P304. The distributor drive gear was worn and would wobble on the cam gear causing a P300. But I kept getting the P304. New plugs, wires, fuel injector spider, etc. Kept getting P304. Drove me nuts. Would only come on when the A/C got turned on. If AC was off and drove very gently, no code. Finally after listening to other people, pulled a compression test and sure enough #4 was low. Burnt valve. Root cause was leaky intake manifold gaskets caused a lean condition. I had the heads rebuilt and it runs smooth as silk with 245K miles.
 

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Discussion Starter · #17 ·
I'm starting to sound like a cranky old man, eliminate the easy stuff first. Before messing with injectors, coil packs etc or guessing about other parts, pull a compression test. It is an easy diagnostic to complete. I will take less than an hour to complete. Once you know things are mechanically sound start going after fuel injectors, coil packs, or other electrical gremlins. If you have lower compression on #1, that will be the root of your misfire.

My sons S10 with a 4.3 kept throwing a P300. A new distributor cured the P30, but promptly got a P304. The distributor drive gear was worn and would wobble on the cam gear causing a P300. But I kept getting the P304. New plugs, wires, fuel injector spider, etc. Kept getting P304. Drove me nuts. Would only come on when the A/C got turned on. If AC was off and drove very gently, no code. Finally after listening to other people, pulled a compression test and sure enough #4 was low. Burnt valve. Root cause was leaky intake manifold gaskets caused a lean condition. I had the heads rebuilt and it runs smooth as silk with 245K miles.
I scheduled the service visit on sunday. I'll keep you posted.

@sparkman yes.
 
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