Rough/Low RPM Unstable Idle

[Anarkistic]

There seems to be a lot of discussion about rough idling on 172s, so as a newbie to the model I thought it best to stop chasing potential fixes and just grab a video to show you folks the way it behaves. In all it's struggling, juddering glory.

That way y'all can hopefully tell me if it's totally normal for a 172 (phase 1) or not. I hope it's not, because it sure doesn't seem healthy. If it's not normal, if you have some idea as to where I should look I'd be grateful!

(The rattling sound is from my exhaust mount that's loose)

Things I have replaced include the TDC sensor, Lambda sensor, ICV, throttle body, spark plugs, coil pack, HT leads and fuel filter. I have also had all injectors refurbed and tested, they're sweet as. No codes except the ABS sensor, no knocking, no misfires, lambda and MAP readings look spot on.

The engine is cold in the video.

Grateful for any feedback!

 

[mumpy]

Does it fully smooth out once warm, or does it always feel a bit lumpy? Can you check fuel trims?

 

[Darren S]

Does it hunt about the lower revs when you pull up at traffic lights and the like, when warm?

Replaced both of the oxygen sensors in mine and that fixed the problem outright. Almost felt like it was about to stall at times, regardless of how cold or warm the engine was.

 

[Louis]

It's really just how they are. Mine used to pop and bang in cold

 

[mumpy]

On mine, after doing everything to it (all ignition related components replaced + ron 98 map that raises idle a bit) and also bringing it to Alex for a timing belt etc. runs quite smooth now even when cold. A lot better than when I first got the car.