[coriolis14]

Hi all -

I have an older E92 (2007; N51 engine/GM 6-speed Auto; ~117k miles) and have been running into a strange engine vibration at idle for the past 3 or so months. The engine will send some moderate vibrations into the cabin while stopped at red lights or stationary in park/neutral that are very noticeable. The revs off idle fluctuate slightly but not drastically so (+/- 100 rpm).

I've gone through the following diagnostics to try and figure out the problem:

1. I've placed the transmission into both neutral and park at stoplights and while idling to see if this was the root cause of the problem - no change
2. The problem never surfaces itself while the car is in motion/not stopped. No bad vibrations while accelerating or coasting.
3. Changing my oil at 115k had solved the idle vibration for about ~1k miles before it resurfaced again (using Liqui-Moly 5w-40).
4. I recently added "Liqui Moly 2030 Pro-Line Gasoline System Cleaner" to my last tank of gas and, shockingly, the issue seems to have resolved itself (no more bad vibrations while idling) since I added this.

I'm thinking maybe there is a problem with the fuel system and/or quality of the fuel I've been using, but I wanted to ask and check in with the rest of the community to see if anyone has run into anything similar before.

[crashoverride]

Old post but a common complaint often happens when the AC kicks in. I'm in the middle of finding a solution myself as it's much more jarring than it's been ever.
Some speculation as to whether replacing spark plugs and cleaning injectors can help.

[coriolis14]

Originally Posted by crashoverride

Old post but a common complaint often happens when the AC kicks in. I'm in the middle of finding a solution myself as it's much more jarring than it's been ever.
Some speculation as to whether replacing spark plugs and cleaning injectors can help.

Thanks for the response - it definitely isn't the AC in my case since it's wintertime and I don't need it. Spark plugs might be the issue - I haven't replaced my plugs in about 40k miles so if this persists then I might have to try it.

Interestingly, the frequency of vibration incidents has stayed low after I switched gas stations from Arco to Chevron. If I switch back to Arco, the vibrations occur. Not sure if there's difference in fuel quality (there shouldn't be in California where all fuel comes from ~8 refiners in the state) or the additive package, but something I wanted to note.