Vibrations can be the mounts perished. Need to get a closer look at them.

For the rpm issue, it sounds to me there's a vacuum leak somewhere. I suggest you use chevron fuel cleaner. If this doesn't help, then the fuel injectors are due for a cleaning.

 

Thanks for the feedback. So you recommend the chevron over the royal purple? I see Chevron has a “complete fuel system” and a “fuel injector cleaner.” Which one were you referring to? I will pick some up today!

 

Either one would be fine and it is a good FIRST step in correcting the problem. May not be the cure but can save a ton of time and frustration.

 

When we think of fuels, most don't look at top tier fuels as much as in the past. We used to stick with chevron, shell, 76, and in some areas BP. There were mom and pops that bought their fuels from some of those same manufacturers.

Some of the smaller stations would buy their fuels due to cost and didn't contain enough fuel and would cause misfires and other issues. I know the lesser was not as refined and had more contaminants that would destroy evap systems because it would cause blockages.

I've tried other fuel injector cleaners, but found that chevron was the best and have continued to use it. @hardtopte72 wrote a DIY to clean the fuel system. DIY 2003-2008 Corolla, Matrix, Pontiac Vibe Toyota... if all else doesn't work, try it out.

Alternatively, costco and chevron tend to be my go to fuels. Others will have their favorites. Stale fuel can do damage as it morphs into something more solid than soluable?

 

If that doesn't work you can try cleaning your throttle body. It could be sticking a bit. If all tune up items fail to address the issue then a compression or leakdown test are an easy and cheap way to rule out a bad head gasket.

 

Similar problem with a 2009 Matrix S with 2AZ-FE. 112k miles. Rough idle in drive and reverse, gets progressively worse when cold (very bad in Minnesota cold below zero F). It eventually gets a bit better when the engine is warm or if the block heater was on for a few hours before. Recently the rough idle has gotten worse even when warm outside or when the engine is warmed up. The engine also seems to stumble when decelerating, but not fully to a stop. I was thinking vacuum leak, but fuel trim difference is no more than 6-7% (LTFT and STFT combined). Troubleshooting below for vacuum leak hasn't helped at all and no vacuum leak actually found.
Spent a lot of time reading and trying to troubleshoot:
-new OEM denso plugs
-removed and cleaned throttle body
-replaced intake manifold gasket with "new" orange one and throttle body gasket
-smoke check without evidence of leak.
-new toyota PCV and vacuum hoses.
-Regularly run Techron fuel injector cleaner
-Checked coil packs with multimeter and all about the same (coudn't find specs) and unplugged individual coils while running with no drop in RPM.
-coolant temperature sensor give correct temp at cold start (correlates with air temp and warms up appropriately).

gas mileage is exactly the same as it has been since I bought 11 years ago. No loss of power accelerating. Runs fine on the highway or when moving at more than just a creep.

Codes are only P0607/P0138 when extremely hot and damp out, these never show when very cold (when the main issue is). Mechanic didnt find anything, just suggested front motor mount "might" need to be changed. Any reason this would be worse in progressively cold weather?

I'm at a loss otherwise other than new fuel injectors. Trying to not just throw parts at it.

Much appreciated

 

Similar problem with a 2009 Matrix S with 2AZ-FE. 112k miles. Rough idle in drive and reverse, gets progressively worse when cold (very bad in Minnesota cold below zero F). It eventually gets a bit better when the engine is warm or if the block heater was on for a few hours before. Recently the rough idle has gotten worse even when warm outside or when the engine is warmed up. The engine also seems to stumble when decelerating, but not fully to a stop. I was thinking vacuum leak, but fuel trim difference is no more than 6-7% (LTFT and STFT combined). Troubleshooting below for vacuum leak hasn't helped at all and no vacuum leak actually found.
Spent a lot of time reading and trying to troubleshoot:
-new OEM denso plugs
-removed and cleaned throttle body
-replaced intake manifold gasket with "new" orange one and throttle body gasket
-smoke check without evidence of leak.
-new toyota PCV and vacuum hoses.
-Regularly run Techron fuel injector cleaner
-Checked coil packs with multimeter and all about the same (coudn't find specs) and unplugged individual coils while running with no drop in RPM.
-coolant temperature sensor give correct temp at cold start (correlates with air temp and warms up appropriately).

gas mileage is exactly the same as it has been since I bought 11 years ago. No loss of power accelerating. Runs fine on the highway or when moving at more than just a creep.

Codes are only P0607/P0138 when extremely hot and damp out, these never show when very cold (when the main issue is). Mechanic didnt find anything, just suggested front motor mount "might" need to be changed. Any reason this would be worse in progressively cold weather?

I'm at a loss otherwise other than new fuel injectors. Trying to not just throw parts at it.

Much appreciated

I did the idle relearn procedure and it’s helped tremendously. It no longer drops below 600 RPM at idle except when turning the wheel at slow speed (like into and out of a parking space).

 

Do a compression test. Cheap and easy to do and will tell you which direction you should go.

 

Update - I tried the idle relearn procedure and it has helped tremendously. It no longer drops below 600 at idle (was down to 500-600). The only time I notice idle fluctuate is when I am turning the wheel at low speed (like pulling in or out of a parking space). Cautiously optimistic, but time will tell. I will update if the problem comes back.

 

Check spark plugs coil packs notorious for problems 1.8 4cyl Yamaha engine

 

Pcv valve too oil problem affect your vvt solenoid on those engine positive crank ventilation easy to change cheap part too

 

I read about switching #1 and #4 coils.....I did it and it worked!!