I have a 2011 Honda CRV with 130k miles and when I am driving, mostly cruising at a stable speed (between 25 and 35 mph), the front of the car will randomly start bucking and shaking very noticably. I can easily recreate the issue every time, if I drive with cruise control on (does on or off) at 35 mph. When it happens, It will go away if I press the 3rd gear button on the side of the shifter. It doesn't change the vehicle speed at all, but raises the RPMs a bit and the shaking goes away. If I slow down or speed up back to 25-35mph it will randomly start up again, until I either speed up or slow down.
Things to note:
1) Engine during those cruising speeds is running a little lean (~2-4% STFT).
2) Spark Advance is normal and not bouncing all over the place
3) Motor mounts are a little bit worn, but not bad, so there is a little vibration when at idle. (None have more than very small cracks in the rubber). I doubt it's this.
4) When at highway speeds, Fuel trim is perfect 0%
5) Vacuum lines look good.
6) MAF reading correctly and responsively
If there is any other info needed, let me know, as for the life of me can't figure out what is happening.
You mentioned having checked the motor mounts. Did this include inspection of the transmission mount?
Yes. Mounts are fine as I can tell.
Check for vacuum leaks, especially at intake manifold.
There aren't any. At least none that I can find. At idle, it runs near perfect. Fuel trim only shows lean when cruising under 35. It runs overall very good. Just not between 25-35.
Have you ever had the fuel injectors cleaned or replaced in 11 years?
I am not the original owner, but I can easily say the injectors have not been replaced and are factory. As for cleaning, yes, I've used that ATS chemical cleaner Scott races about, because my car was initially running slightly rich when I got it and made it run good after.
I will also update that my STFT does not change at all when the shaking starts. It just sits at 0-0.8%, so idk lol.
I was referring to removing and pressure cleaning the injectors. When were the spark plugs last changed?
Haven't done that to the injectors yet. Spark plugs where changed 2 months ago, as I thought they were the culprit of a previous issue I had (bad plug). Those plugs were in immaculate condition.