# Engine "knock" at low RPM under load



## Manville69 (7 mo ago)

Hi everyone. For a little while now, my '11 Cruze with the 1.8l 6speed, has a knock at low RPM under load. It also clatters under load while accelerating until the RPMs pick up. Usually from about 2500-3500. After that I cant hear it, either it due to engine noise or the sound disappearing. I've replaced the tensioner pulley and belt cause I thought that might be the culprit, it wasn't. My dad thinks it might be a leak in the exhaust manifold. I recently replaced the oil cooler gaskets and replaced the manifold gasket when I had it off. The noise is still there. It could be a crack somewhere. The sound does not occur while I rev it. It also does not occur when I have easy accelerations so I don't think it's a lifter issue. I've uploaded a video to YouTube. What do you think it might be? 2011 Chevy Cruze 1.8l clattering.


----------



## jblackburn (Apr 14, 2012)

Dual mass flywheel maybe?


----------



## Manville69 (7 mo ago)

jblackburn said:


> Dual mass flywheel maybe?


Hmmm. Perhaps. I've never driven a car that had a clutch or flywheel go bad. Other than the sound, do you know of any other symptoms of a worn flywheel on the Cruze?


----------



## jblackburn (Apr 14, 2012)

Manville69 said:


> Hmmm. Perhaps. I've never driven a car that had a clutch or flywheel go bad. Other than the sound, do you know of any other symptoms of a worn flywheel on the Cruze?


Jolty transitions on/off power like a bad engine mount.
Grinding sound when clutch pressed in between gear changes.
Horrible vibration at idle

The symptoms in my case would come and go, but high load and high heat would make it show up in my car whenever I was up in the mountains. Let the car sit overnight and it acted completely normal again. One day the thing just locked up and knocked all the time/shook the car terribly.


----------



## Manville69 (7 mo ago)

So I do have a slight shaky idle. Nothing serious yet. However, when I do start the engine cold, I hear something vibrate rapidly for a second or two and then it stops.


----------



## jblackburn (Apr 14, 2012)

Manville69 said:


> So I do have a slight shaky idle. Nothing serious yet. However, when I do start the engine cold, I hear something vibrate rapidly for a second or two and then it stops.


Maybe a VVT cam gear not locking until oil pressure builds up.


----------



## Manville69 (7 mo ago)

Update: I had some people look at it and said it sounded to them like carbon build up on the valves. I ran some high premium, non ethanol fuel and as a start, some Seafoam upper engine cleaner about 3 weeks ago. I also had been doing high RPM driving to help clean as well. It got rid of about 90 percent of the noise. I may do another cleaning in a week or so and change out the spark plugs (even though I replaced them about 20k miles ago) to reduce the chance of fouling them out. I'll try and make an update later for any additional changes.


----------

