Mk1 172 rough idle

[Wurlie]

Dear all,

I have done 30k miles on my Mk1 172, and it has developed an intermittent stutter at idle, as well as a slight decrease in performance. It seems as if every so often one of the cylinders misfires. Any ideas as to what this might be?

Thanks very much!

Wurlie

 

[matt4478]

Hi Wurlie - my Mk1 172 was a bit rough idling last week (also approaching the 36k service, so its kind of acceptable really!) so I changed the air filter and also cleaned out the throttle body (around the butterfly valve) as it was full of crud/oil and it seems to be running nice and smoothly again now. Performance seems a little perkier too, so thats a welcome bonus!

Yours sounds slightly worse than mine though, as I didnt have anything like a misfiring cylinder, it just felt lumpy really... Maybe its not the solution, but its certainly something to have a look at - Hope that is of some help!

Matt

 

[Simon172]

Possibly a knackered coil ? i rang my garage and they told me the problem im having with mine was related to that, apparently a common fault with them? Basically - my car would lose all power and splutter/stall. Id pull over and thered be a large smell of catalytic converter eggs type. Turn back on and itd be kinda ok.

 

[Wurlie]

Dear Simon, Matt,

thanks for your replies. It seems tha there is another 172 of the same vintagge in the garage I go to. The service manager does not seem to be able to find a fix. First they said that one of the injectors was clogged, so they changed all four and charged me for that only for the problem to come back!

I also have a feeling that one of the coils might be tha culprit, bit am still waiting for them to call with a fix!

If you have any more ideas, please do let me know!

Many thanks, Wurlie.

 

[RobFenn]

If it was misfiring the garage should be able to tell whats gone wrong on the diagnostic machine. The exhaust monitors what comes out and the ECU adjusts everything based on that. If the air/fuel mixture was buggered in the slightest one of the many sensors would go mental and youd have a warning light up. I presume its something completely different from what you think then, but i have no idea what it would be! Sorry!

 

[jimblive]

mine has done around 33k and is also very rough when idling, it is due its service so hope that sorts it out.

 

[swelch]

mine has done only 5k miles and has a lumpy tickover. Reno changed the brake switch (on the pedal) and said it was fixed !!!!! No its not, its still lumpy.

 

[RobFenn]

Is it a definite development opposed to being there from the start?

 

[Wurlie]

Hi,

it was there from the start, but now seems more prominent.

Just heard back from the dealer, of course they now say that they all do that. The other 172 they had in the garage had a clogged up cat, which they have fixed and now say that it idled in the same way. I am not particularly happy.

I will get a Supersprint system in two weeks and see if that alters anything, with a cat replacement pipe on the way a week later. Then I might look into ECU reprogramming. Although I really do not think that I need more power, more just to cure the idling problem.

Best, Wurlie

 

[RobFenn]

Well there is this 172 4000rpm trouble, maybe its linked to that? Its the centre section which is the problem for that

 

[Simon172]

Probably a clogged cat then. OR the coil being faulty as you mentioned. All 172s are quite lumpy on idle due to the cams being quite wild apparently....?

 

[Wurlie]

Hi!

No, definitely not the 4k rpm rattle - I have dealt with that by removing the centre section of the exhaust and fitting a straight pipe.

The cats are ok for sure. As I said, when the Supersprint system is fitted, I will see if there is any change to how it runs on idle.

The cams change in profile higher up the rev range, so the low rpm behavior of the engine should be as docile as that of std. 2l Renault engine, as fitted for example to the Megane.

Does anyone know where the coils are located and how they can be tested?

Thanks again, Wurlie