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ANOTHER lumpy 172

  Clio II P2 172
Hi all!

Hoping for some suggestions on what to check out to narrow down my idle issue.

I recently picked up a P2 172 that’s done ~180k kms.

Since I’ve owned it it’s had a pretty rough idle, which I’ve heard is common on these cars but recently it’s gotten worse to the point where it stalls easily while reversing.

The car runs perfectly once it’s moving, but during idle it sounds like a boat. It doesn’t hunt, the needle stays steady, it won’t die while stopped and starts with no issues.

Previous to me owning the car, the belt & dephaser were replaced less than 10k kms ago, and I’ve been assured by the mechanic that did it that the timing is correct, was done by some French specialists here in SA. At the same time the coil pack, leads & plugs were inspected, but just the plugs replaced.

I’ve replaced the injectors because they’d never been replaced and we’re looking a little tired, this improved the way the car drives, but not the idle.

I have an RS tuner so once I’m home from work I’ll get some live data so that hopefully someone here can better diagnose.

What live information is needed to better identify an idle issue?

Any help you can offer would be hugely appreciated :)

So far I have;
  • Lambda Sensor Voltage
  • MAP Sensor reading

    Once I’m home this evening I’ll post the results and like I said, hopefully someone more knowledgeable can help me diagnose. Cheers!


ClioSport Club Member
Check map sensor readings are around 400mbar on idle, that will give you an idea if cam timing is correct. Also should read around 1000mbar atomspheric pressure with ignition on engine not running.

Lambda voltage on pre cat sensor should rise and fall fast over 0-1v scale from memory as narrowband.

Id do a compression check first to make sure engine is healthy and check no vac leaks on plenum, ht leads are routed correctly and not arching out.
  Clio II P2 172
I don’t have a tool to do a comp test unfortunately, will get one this weekend.

Thankfully the leads looked okay, couldn’t hear any leaks on the plenum, nothing obvious either.

  • Lambda mV jumped up and down from ~300~700.
  • Ignition on, atmospheric pressure was 1028mbar.
  • At idle, MAP was reading ~484 > ~513


ClioSport Club Member
Doesnt sound too bad. As above compression test to see if any internal issues with the engine. If all good just save all parameters on Rstuner and check air temp, coolant temp sensors for any erratic readings.

If you have access to can clip, assuming all sensors reading ok, id clean throttle body and reset fuelling adaptives and throttle settings and let the ecu relearn, might cure it.