Car in question is a Renault Clio B 1.2 16V with about 85KKm. I experience two issues:

  1. Intermittent starting problems, independent of hot or cold engine. When the problem occurs I need to press the accelerator to get it to fire while cranking. Afterwards the exhaust smells of fuel.
  2. Intermittent high idle on hot engine.


  • There is no MAF, just a MAP-sensor. I do not have charts but I remember seeing constant negative pressure while idling. I will provide further data.
  • Last time I checked the spark plugs they seemed to be in order. I will check them again today and provide further information.
  • There is no active CEL, nor there are any stored fault codes.
  • The O2 values seem to be acceptable: enter image description here
  • Not so for the fuel trims: enter image description here
  • At the moment I have no possibility to check the fuel pressure. The fuel filter never got replaced. Since the change interval for the filter is 240KKm (actual mileage: 85KKm) I want to exclude the filter.


What would be a possible explanation for the high fuel trims? Perhaps the MAP-sensor or the IAT sensor? I'd like to exclude the O2 sensors as the values seems right (at least from my limited perspective). Could somebody purpose further checks?

  • The rear o2 is at operating temp and CL? That's too low for idle or cruise, .650-700mV is normal for most any engine. If it were a GM I'd say it was stuck at or close to reference voltage or there's an exhaust leak. KOEO engine cold does IAT match ambient or close enough? Does the ECM utilize a clear flood mode at 100% TPS KOEC? Test for vacuum leaks? Have you tried resetting learned values? After driving and letting the car sit for however-long pull a plug and look for fuel in the cylinder. Also I don't know about those fuel trim numbers. Total fuel trim of at least 86?
    – Ben
    Aug 4, 2018 at 0:03
  • Seems implausible that it's not setting a code. What does Renault service info say about the trip conditions for the monitor? Or can you confirm the numbers with another scantool?
    – Ben
    Aug 4, 2018 at 0:07


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