Hello everyone.
I have a 2013 Acura RDX V6 AWD with 270,000 KM (168,000 miles). Timing belt spark plugs ect changed 4 years ago at 100,000 miles interval.
Problem started couple weeks ago, at Idle around 600RPM in park and in drive every few seconds the car would rev up very slightly, the needle moves up just a bid, nothing crazy. AC is off. I can hear the engine rev up. The exhaust would make a buff noise when the needle goes up.

I used to get gas mileage 10.1L/100km, but since 10.8L/100km. There's no check engine light. I plugged scanner in, and there was no code.

Anyone can give me some suggestions?

 

Is the air intake duct intact? Is the throttle body clean? Is the air filter clean? PCV valve good?

 

Ditto on this. If the RPMs fluctuate around 200-300, I wouldn't worry too much. However these things that @altair47 mentioned are all what can affect your gas mileage. If it's cold outside, your RPMs will be higher on startup.

 

I cleaned throttle body with throttle body cleaner. I also cleaned the MAF sensor with MAF cleaner.

The PCV valve was badly clogged with oil slug. It was still rattle. I replaced with new OEM Honda PCV valve (171300-RCA-A02)

[size=13px]I checked all ignition coils with multimeter and they are all good. The spark plugs on the outside bank are good, just a bid of oil on the threads, tips are good.[/size]

For the inner bank, the first spark plug on the drive belt side was badly fouled with oil, very black. The other two got some oil but not too bad, the tips are okay.
I replaced only 1 fouled spark plug (NGK 7751Laser Iridium). The engine runs very smooth now, no fluctuation.
I didn't replace all the spark plugs as I wanted to monitor if the PCV valve stops the oil fouling.

 

Then you have problems with oil consumption and you need to install a S-VCM Controller.

 

@altair47 Is this the muzzle you referring to? https://www.svcmcontroller.com/

Does anyone know if there's a Canadian dealer?

 

Send them a message through the website