Slightly grumpy idle - 172 cup

[SiH]

Afternoon all,
I picked up a 172 at the weekend - lovely car, great on the test drive, but after I get it home, I noticed the idle can sometimes be a little rough (it wasn't on the test drive!)
Still sticks around 1kRPM, but seems a little off beat and chuntery at times.

Car has the belts and dephaser done less than 600 miles ago by a reputable specialist, so I don't believe it to be a timing issue. Also had new plugs at the same time.

Doesn't show any hesitation under load at all, so I'm thinking coil(s)/leads are fine. It's literally only on idle.

Only modifications I'm aware of are an aftermarket filter. However, I'm wondering if it has been remapped - chiefly because when (very cautiously) checked, it doesn't appear to have a limiter in place! Well, certainly not below an indicated 7.5k anyways, I wasn't willing to take it any further. I'm wondering if this suggests it may also have more work done I'm not aware of, like more aggressive cams, which may be the root of the issue. I guess I should take the rocker off to look.

 

[Addicted]

Sounds pretty normal tbh, they also idle worse without the "RSTuner map" - the most common map, though it sounds like you have some sort of map with the high rev limit!

 

[SiH]

Ah cool, OK, thought that may be the case - not that familiar with these engines but I've seen references to them not being the smoothest of idlers!
The other one I viewed (182) was similar, but I just put that down to the fact it was a shed.
Cheers

 

[Diagro]

I was wondering the same when i got mine last sunday.
But as far as i can tell and after seeing two other 172's in traffic yesterday it seems very normal.

 

[SiH]

Just done a bit of googling - if it has been remapped, does that mean I should be running it on super/'98 RON?
Being from a rotary background, I'm all to aware of the dangers of pre-detonation...

 

[N4TH4N]

Many different opinions on that. For me my car is less lumpy running it on vpower fact

 

[Addicted]

I would run it on higher RON yeah, it'll run better then anyway!

Before I got mine remapped, running on 98 as opposed to 95 changed the idle to be much better, and its better again on the remap

 

[MartinR]

Should be run on 98 ron wether its mapped or not!!

 

[SiH]

Really? Is that the official line from Renault?

 

[ed55j]

Should be a sticker on the inside of the fuel cap which says 98ron

 

[SiH]

Coolio, will have a look, didn't know that

 

[Marcos999]

I picked up a 182 in a mess a couple of weeks ago, it had bugger all fuel in it so I put some 95 in and it really didn't like it. It wasn't until I washed it the next day I found the 98 ron sticker so next fill up I used super unleaded and it runs a lot better. The idle is still a bit lumpy (although I think mine is a bit low) but getting that much power from an N/A 2L is going to come with a bit of a compromise.