# Rough idle no code after engine rebuild



## Hunterderjunge (Oct 11, 2021)

JohnBee said:


> 2018 Chevy Cruze started running rough and throwing missfire codes, get it checked out and found that the car was spitting oil at the crank seal, and cylinder 1 had lost pressure.
> Luckily, the car was under warranty and we were able to get the top end rebuilt by the dealer, however and as it turns out, the car is idling rough, like it wants to stall - brought it back to the dealer and was told they could not find anything wrong with the car, and so they put an engine treatment into it and called it fixed. Though the car still won't idle right and sometimes struggles to start following the auto/stop function.
> 
> With that said and after a few calls with the service dept, I decided to get an ECU with torque and found that (1) of the 2 oxygen sensors is showing intermittent voltage, whereas the second is stable, and so I wanted to ask if anyone could confirm if this was normal behavior or not on these cars?
> ...


What is 'intermittent' voltage? Sensor 1 (upstream) should jump from 0.1-0.9 volts very quickly. That's normal, as the fuel trims are constantly changing. Sensor 2 should stay close to 0.5 I believe, and stay relatively stable. Shouldn't have more than +- 0.3-0.4 volts of variation. Personally mine sits at a steady 0.6-0.8 volts, but that's because I'm missing a cat.


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## Barry Allen (Apr 18, 2018)

Cylinder 1 problems?

Is there a chance you have a cracked piston?


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## alexandru96 (7 mo ago)

JohnBee said:


> I decided to get an ECU with torque and found that (1) of the 2 oxygen sensors is showing intermittent voltage, whereas the second is stable, and so I wanted to ask if anyone could confirm if this was normal behavior or not on these cars?


bank 1 sensor 1 = upstream sensor (the one before the cat) and it should jump up and down (the higher the voltage that the sensor produces the less the oxygen in the exhaust gas) 
bank 1 sensor 2 = downstream sensor (the one after the cat) that, at idle or accelerating should stay more or less stable

As for the rough idle and car wanting to stall at idle (or even while driving if it is worse) i've have had the same issue with my '10 cruze 1.6 non-turbo, on LPG it had some pretty violent misfires during idle (it felt like a kick basically) and while cruising around sometimes it was jerking back and forth pretty violently, on gasoline these symptoms were not as noticeable but still they were. The fix was simple, I've replaced the ignition coil, since it's a old car I've bought the cheapest aftermarket coil I've found, changed it and that fixed the issue right up


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