I have just bought a second hand Mazda cx5 2L.
I have noticed an annoying rough idle when the car is standing (in a traffic light for example) on both D or N (with and without A/C, with disabled I-stop)
In happens in cycles of about 20-30 seconds.
The engine is at 800 RPM, it goes down to 600 rpm and then there is a small shaking and the RPM climbing back to 800.
There is no check engine lamp.

has anyone encountered this phenomena and succeeded to solve it?

Thanks.

 

I've noticed it on both cars that I drive (Turbo & Naturally Aspirated). It's just the way these cars behave.

 

So they still offer the 2.0l in other countries I see.

 

Basically yes. But this one is from 2020 not a new one.

 

I can't accept it's a normal behavior. Not all mazda CX5 owners have it.
I read some forums, and it seems (not sure), it's because carbon powder in the intake manifold or in the throttle.
I am still following the relevant thread. If they provide a soluton, I will share it.

 

The ECU adjusts for the gasoline that is used. So ya its normal. The only way to control this is to use only top tier gasoline and the highest octane available. Although the Mazda current engine can and do run well on lower octane fules they DO NOT run smooth consistently at idle on the lower octane fuels.

This argument seems to be on many Mazda forums but the anyone that simply watches several PIDs in the ECU and experiments with octane values can see data that we could call empirical in nature how the ECU will adjust to less then the highest octane fuels and lower quality fuels.

The other thing is the misconception that spark plugs will give the best performance with mort then 30k miles on them. Sure they will last that long or longer but their spark energy starts to dimmish influenced by several factors that slowly reduces performance of the engine including MPG and drivability like a smooth ide with and without AC.

Lastly if you Mazda still has less then 15-20K miles it is not likely the engine is even broke in yet. Any engine that is not broke in will have some RPM fluctuation that can be felt and noticed on the tachometer at ide.

As for anyone or forum talking about carbon in the intake system and in the combustion chamber unless they scope the intake (had to do because of the configuration of the runners and the combustion chambers it all BS!
Besides the carbon would be caused from with a incomplete burn of fuel in the combustion chamber or oil from the PCV getting into the inductive system both can be seen by properly reading the spark plugs or by watching the timing, HO/2 voltage and CAT temperatures. Or by doing some data logging on multiple ECU engine control areas using an oscilloscope. . None I have seen from those other Mazda forums. So its about arm chair DIY guessing and speculating BS theories. IMHO

 

I don't have that issue in my 2020 but I dump in a good fuel system cleaner during a fill up roughly every other month.
I have had too many fuel injection issues in past vehicles (mainly clogged injectors) to not do this.
I don't have actual scientific studies to show it works but I've had no fuel injection system issues with any vehicle I've used it in.
Excluding a 2003 BMW K1200GT motorcycle but that was a fuel pump failure of which the fuel had no bearing on.

 

Yup!

I have said a few times on this forum that using a fuel additive once in a while like Chevron Techron or STP is a wise idea and help support preventive issues.
The top tier fuels are either Chevron or Shell the rest seem to fall under these 2 when you look at the formulas used by each.
I prefer Chevron but do use Shell and occasionally Union76 when on road trips. But incase none are available I do carry fuel additives both octane boosters and F/I cleaners.

 

Agreed. I always throw a bottle in my vehicles every oil change.