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2013 Cruze 1LT
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Discussion Starter #1
So I’ve been trying to diagnose a rough idle at startup for awhile, only happens on a cold engine. Decided to take a look at the pistons today. I was shocked to see them wet and maybe covered in oil. Plugs are dry but maybe a bit black. Fuel injectors are new as I thought I had a leaky one as it sat overnight. No CEL and no noticeable smoke out of exhaust. no noticeable oil use on dipstick or coolant from reservoir. .

Does this look like oil to anyone else? Pretty nervous about my find. Car runs great otherwise. Very low misfires on tuning logs.

Any ideas are appreciated.


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2013 Cruze 1LT
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612 Posts
Discussion Starter #2
Update, idled it for 30 seconds, pulled a plug and cylinder inside looked exactly the same. Figured it may burn off or something.
 

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2013 Cruze 1LT
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Discussion Starter #4 (Edited)
Wet or clean pistons is not usually a good sign.
Yeah... I figured, those have 57k on them. I thought at first an oil ring on the piston, but its all 4 pistons... likely all 4 didn’t go bad. I have some fuel system cleaner in, but I doubt it works this good... and the piston tops still shouldnt be wet.
 

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2014 LT program car, Pull Me Over Red
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Yeah... I figured, those have 57k on them.
So you had rebuilt the motor at some point? Could be the rings are shot due to bad hatch job or maybe the openings are not rotated correctly etc. I have not had this motor apart yet so I am thinking back to my V8 days.
 

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2013 Cruze 1LT
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Discussion Starter #6
So you had rebuilt the motor at some point? Could be the rings are shot due to bad hatch job or maybe the openings are not rotated correctly etc. I have not had this motor apart yet so I am thinking back to my V8 days.
No, that’s all my 2013 has lol! Bought it CPO from dealership.
 

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2013 Cruze 1LT
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Discussion Starter #8
The turbo to intercooler hose and charge pipe to throttle body has quite a bit of oil, I wonder if this is turbo related instead of engine block per say? They are slimy but maybe that’s normal.
 

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2013 Cruze 1LT
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Discussion Starter #9
Went out on my work break and stuck one of those big dog ear qtips down, dabbed it up and its fuel, I am almost 99% sure. Strong odor when its wet and as qtip dries smell goes away. So I am feeling more confident in things, but why are all 4 so wet with fuel and plugs are dry? Seems its firing the injectors when the engine is off, but I hear no clicks. I have heard a high pitched squeal/whine that goes on and off for about 10 seconds randomly since owning the car, wonder if it’s related. It’s an electronic sound and seems to come from the PCM area.
 

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So I am feeling more confident in things, but why are all 4 so wet with fuel and plugs are dry?
I'm thinking you have leaking fuel injectors, and they are leaking after power-off, until the residual fuel pressure subsides.

That would explain the dry plugs but wet pistons.

Unresolved, and not on my resume, is what's causing them to leak. Could it be bad injectors?

Is there some sort of in-between voltage - ie, an invalid level somewhere between off and on - that's causing them to slightly open and hence leak (until the fuel pressure drops)?

Or is the computer, for some unknown reason, sending out some extra pulses to each injector after engine shut-off?

I'm not sure what test features are available on automotive test equipment, but I'm thinking an oscilloscope or maybe a volt meter might be useful in isolating the cause.

Doug...wondering out loud...

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2013 Cruze 1LT
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Discussion Starter #11
Thx for the reply Doug and Blas, I may buy a set of cheap eBay ones to throw on and test (Yes I said test, not use daily lol). I assume this is why my turbo was covered in soot as well as the inside of the downpipe, it’s running very rich and starting with fuel in cylinder. This also explains the rough idle at startup. I assume once warm the fuel vaporizes if it leaks onto the pistons, warm starts are fine.

I dont think its BNR tune related, but I have since flashed the stock back on.
 

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With wet pistons. That's a flooding condition and should require wide open throttle for clear flood mode to start up.

You should also see exhaust smoke on startup. What color it is will tell you.

You'll have to stand behind the exhaust and let someone else start engine up. It's probably not heavy enough to see out the rear view mirror.
 

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2014 LT program car, Pull Me Over Red
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Thx for the reply Doug and Blas, I may buy a set of cheap eBay ones to throw on and test (Yes I said test, not use daily lol). I assume this is why my turbo was covered in soot as well as the inside of the downpipe, it’s running very rich and starting with fuel in cylinder. This also explains the rough idle at startup. I assume once warm the fuel vaporizes if it leaks onto the pistons, warm starts are fine.

I dont think its BNR tune related, but I have since flashed the stock back on.
I would tell him about the issue and see if in fact it is tune related as that is an area that is tune-able.
 

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