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Discussion Starter · #1 ·
Hello!

Thought I was done with issues but I found one more :)

I am not using the ac. Turned it on and still the idle issues persist and are unchanged. No check engine light...I repeat...no check engine and no ac.

2012 cruze 2LT automatic transmission. 1.4T. 86k miles

I changed some parts on my cruze and there's some kind of weird idle going on. Only happens when the engine is hot. It normally idles at around 800 rpm, but it keeps dropping to 500ish and the car starts vibrating. I replaced the valve cover a while back because the part I had was discontinued, and I figured it was going bad again. Changed it, idle is still dropping. I replaced the purge valve solenoid and my clicking noise stopped but the idle still drops. I called my dealer and they asked if the battery was ever disconnected and I said yes. He told me to do an idle relearn but he said he didn't know how... yeah....

Anyone know how to do the idle relearn? Im about ready to just put a new throttle body on it or try to find the IAC if it has one. Newer cars are baffling things lol.
 

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Discussion Starter · #3 ·
Oh this is embarrassing. I guess it's the o2 sensor. Gonna replace both of those. Sorry about that everyone...thanks.

I still have no idea what an idle relearn is, never had to deal with it before. Not on the service manual that I can see.
 

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I know idle re-learn was something you worried about on older computer cars. I'm not sure as it applies to the Cruze.
 

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Yeah, it sounds like either a MAF or O2 sensor issue (or a leak somewhere in between). Are there any pending or stored codes for the O2 sensor?

Most cars re-learn the idle within a drive cycle after disconnecting the battery. When I put a new battery in the Toyota, it quit dipping the idle after the first two stops.
 

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Discussion Starter · #6 ·
I'll check pending codes when I get the chance, gonna have to get my dad's scan tool. I really thought it was the valve cover but I came across an article here about an o2 sensor replacement for a similar issue and it doesn't hurt to replace then but I guess it helped a lot lol. I didn't notice any stumbling or hesitation. It did kind of jerk uphill sometimes kind of hard to describe what was happening there. I'll see if that's gone too. Ugh I grew up fixing cars and I don't understand this one at all.

Thanks for the help! I don't see mention anywhere of an idle relearn so I'm not gonna worry about it. Car seems happier and doesn't make that loud click to boot.
 

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If you want to save yourself a little bit of $, you can generally just replace the front sensor. The post cat sensor more or less just monitors the catalyst output and depending on the ECU, has little to no impact on actual engine control.

I don't even know off the top of my head how much a Cruze O2 sensor is, but seems like parts are *much* cheaper for this car than my European one.

So you've already gone through the replacement and that took care of it huh? That's good to know for other members - I can think of at least two that had this weird idle hunt happen after a valve cover. I'll see if I can dig up their threads. Wonder if the oil being sucked through everything helped foul that sensor.
 

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Discussion Starter · #8 ·
Yeah just the front one. Cost $52 at a local autozone. I had it off before to check the turbo I should have replaced it then, didn't occur to me.


I had a 97 Lumina at around 170k it threw I think 6 codes at me and it ended up being the o2 sensors. I am not sure why it didn't throw a code, I'll monitor it I guess.
 

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Discussion Starter · #9 ·
What's weird is I can recreate the issue when I'm standing still, if the windows are all the way rolled up and I pull the driver's door switch buttons up for the two rear windows the car shudders and rpm drops for a second, which makes sense I guess because it's drawing power. That's what's getting me here it was doing the same thing at idle. I'm skeptical but I'll see what happens.
 

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What's weird is I can recreate the issue when I'm standing still, if the windows are all the way rolled up and I pull the driver's door switch buttons up for the two rear windows the car shudders and rpm drops for a second, which makes sense I guess because it's drawing power. That's what's getting me here it was doing the same thing at idle. I'm skeptical but I'll see what happens.
Huge load on the alternator since the window regulator isn't going anywhere. I think I recall that mine dipped a bit too when under a sudden electrical load.
 

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Discussion Starter · #11 ·
Hmmm okay it's still doing it. The car is happier but it started doing it again. One thing I didn't check was the cooling fan, I wonder if it's cycling. I really think it's a power draw somewhere. I remember someone telling me that it has 2 coolant temperature sensors and one went bad on theirs causing the fan to constantly start/stop. It's not the compressor, rechecked it.
 

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Discussion Starter · #13 ·
The compressor runs when it's on defog which is what I used to test it.

My car doesn't pulse/jerk uphill anymore so that's weird. Whatever I'll just wait for an engine light, I don't want to keep guessing I have no idea how modern cars work lol.
 

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Discussion Starter · #14 ·
Update: Took the throttle body off and cleaned it, it was pretty bad. Put in a new MAP sensor as well. Seems to have helped but I'm still testing it out. (MAF cleaned as well).

Another dealer had no idea what they were talking about concerning an idle relearn. Car idled high for a bit, wandered around then settled after reinstalling the throttle body.

It still drops a little when coming to a complete stop but then it's totally fine. My jerking uphill is completely gone and hasn't come back.
 

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Discussion Starter · #15 ·
Hello!

For the most part the idle issue is gone. I put another o2 in lol the one before the cat. When I come to a complete stop it does a small bounce and then it's fine. :)
 

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I had the same issue. Took it to the dealership and they could not find anything wrong. Still happens every once in a while don't know how to correct the problem.
 
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