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Issue

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.

Diagnosis

  • 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.

Question

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?

Improve this question
2
  • 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 '18 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 '18 at 0:07

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