172 miss fire?

[french fanatic]

hello all, never been on here and need some help, i got a clio 172 and its been a absolute gem, apart from last week, its started miss firing and runs lumpy from 0 - 4k revs, tried replacing the plugs, ht leads and coil pack and its still doing it, got it plugged in to a diagnostic and nothing it wrong. help

 

[mr.pink87]

Could be a oxygen sensor issue. Try swapping the pre and post cat sensor and see if it´s getting better!

 

[french fanatic]

ok mate il try that, a mate said it could be a valve ?

 

[mr.pink87]

A valve!? If a valve would be damaged you´d have more problems than misfiring. I´d say lambda issue because you say it misfires between idle and 4k and this is the closed loop window.

 

[Trainerbrow]

as above, do a comp test

 

[MicKPM]

I'm not saying it is but I am saying don't rule it out as I've seen poor running caused by a weak/bent valves on a couple of F4R Clio II's now which both cases ended up destroying the block, piston, cylinder head as the owners carried on driving them agianst my advice somehow hoping the car would fix itself.

To be safe have the engine compression tested as a matter of urgency as mentioned above and if one cylinder is giving lower readings than the others then the head needs to come off and have the valves on that cylinder inspected/replaced ASAP... do not ignore it and continue to use the car!

If they are all balanced and pushing around the same level then that's good news and it would be worth getting the car back on to the diagnostics, only this time, kick the previous guy out of the driving seat and get someone that knows what they're doing to look over the live data feeds to tell you if the H02 (or other sensor) is looking suspicious as generic fault codes and looking specifically for them is not carrying out proper "diagnostics".

Mick