Air/Fuel ratio

[Chemist]

Hi guys, i'll try and put this down in not too many words.
Last year had con rod bearings gone with some serious crankshaft damage. New engine installed, now done less than 5000 miles. Remap still present on the ECU. Some time before the engine went, I had a wide band Air/Fuel gauge installed, brand: PLX Devices. The accompanying sensor is of the self-calibrating type (so I've been told). Never had any weird readings up till now. Normally under 'granny' driving conditions I'd get everything between 14.7 and 15.8 [which is OK for an atmo engine], during warming up sometimes leaner [16.5] and on full throttle [last 1000 rpm before limiter] as rich as 12.2~12.4.
A few days ago the gauge started giving me readings of 17 to 18 during normal cruising sometimes leaning out to 19. :scared: :scared:
Then the other day everything was back to normal.
Today during idle again 17.5 to 18 leaning out to 19 during cruising. I get no abnormal hesitations from the engine, no weird noises.

So, could be the wide band sensor is faulty, could be a problem with the MAP sensor, could even be a vacuum problem in the manifold...

My question: suppose the sensor isn't faulty, shouldn't the Clio's Sagem 3000 pick something up and throw me a fault code on the dash, especially running this lean?

 

[Foxspeed]

if it runs too lean it will run poor and start to have mis-fire issues etc

its probably worth trying to get another independant reading from the exhaust from another source just to see if the calibration is ok on the wideband one

 

[Chemist]

Yeah, that's what I'm aiming at Fox.
At the moment my tuner is very very busy as a few of his employees are ill at home. He's overloaded with work [no sign of economical crisis in tuning-land it seems] for the time being. My neighbor provided me an OBDII-reader (Turbogauge) but I can't figure out if the bloody thing can give me an A/F reading [or lambda]... anyway, no misfires detected and no abnormal fault coded stored [except for the cat error P0240 due to the 100cell race cat].

Don't know if my dealer can use the genuine Renault CLIP tool for determining A/F; perhaps Lamba can be measured [A/F=Lambda x 14.7]...

 

[shakey_hand_man]

just to add a thought. on over-run fuel will be cut completely, so off throttle you could potentially get very lean readings...

 

[Chemist]

its probably worth trying to get another independant reading from the exhaust from another source just to see if the calibration is ok on the wideband one

Went to my dealer's this afternoon for a complete emission check, including Lambda. Everything turned out fine. Lambda just a tad over 1 (1.006) corresponding to A/F 14.8. The A/F gauge told me differently. According to that I'd be idling on plain air (A/F 20 = Lambda 1.36).
Glad my baby's in good health and it wasn't a burnt valve, MAP sensor or manifold prob.


To my surprise all emission values were in spec. Seems when heated up like it should, the 100cell race cat works flawlessly.