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Intermittent stalling - Have I got a dudd O2 sensor? - ECU/Freescan/Espritmon - The Lotus Forums #ForTheOwners Jump to content


Intermittent stalling - Have I got a dudd O2 sensor?


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Now that my Esprit is running again - albeit not roadworthy - I've noticed that from time to time the car seems unable to hold idle while running in the garage. It doesn't do it all the time, but when it does the car will start and run for maybe a minute before the idle gets lower and lower until it stalls and will continue to do it on repeated restarts. I can leave it a couple of hours/days and then it will be fine again and then next time it may or may not start stalling again.

I went out with the laptop and ran Espritmon to see what was going on yesterday and in typical fashion initally the car behaved itself. I left it for a couple of hours and came back again and I was able to catch it in the act. From comparing the charts to my untrained eye the only obvious difference I can see is the behaviour of the O2 sensor. On the good run once it goes closed loop the O2 reading is rapidly oscillating around the 0.5V mark, however on the run where it stalls the O2 reading looks a lot less "busy", for want of a better word to describe it.

Before I go and blow £50+ on a new O2 sensor I've attached the Espritmon logs from a good and bad run to see if anyone else has a different view on the log data.

 

Log from cold start where the car behaved: esprit_6_5_16_7_25.log

Log from a "tepid" start a couple of hours later where it stalled: esprit_6_5_18_35_53-stalls.log

Norfolk Mustard S4s #1 :)

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Tom, not an expert but when similar things happened to mine I noted from the Espritmon logs that when it goes closed loop, the O2 sensor should be providing its 'wobbling about' signal. If it shows going closed loop and the signal is not wobbling around (i.e. it's just acting like a (temperature dependent) resistor then that's when the trouble starts, it's expecting a real O2 reading, but just gets a resistance reading. I replaced my sensor and totally resolved the stalling issue. Your log where it works shows the O2 sensor going wobbly shortly after going closed loop, not exactly when it went closed loop, maybe just lucky that time?

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I believe the Zirconium in the sensor needs to attain a certain temperature before it reads the O2 level (O2 partial pressure). The sensor has a heater within it to get it up to that temp quickly. Maybe that heater is buggered. If it runs/idles long enough for the exhaust to heat the sensor up to the required levels, then things normally are OK from then on.

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I've seen the stalling behaviour occur from both cold and hot starts, but in both cases it doesn't happen every time.

If there is heater within it and its starting the fail causing it not to work all the time that could explain the symptom I guess.

Norfolk Mustard S4s #1 :)

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I have to ask (again)

 

Do ROW GM MPFI Esprits have a roll over valve in the RH sail panel? I KNOW that USA models do.

 

I have seen the ROVs get sticky from long periods of Esprit dis-use. That can cause the type of intermittent issue you are experiencing. (Our car had an idle issue on hot starts and that is what the issue turned out to be.)  I was fighting the issue (which only happened maybe one a MONTH) for over three years...

 

 

Atwell Haines

'88 Esprit

Succasunna, NJ USA

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I bought a new O2 sensor and a rollover valve since it was only £9.

I've only fitted the O2 sensor for now and its started and run without stalling, but given its an intermittent fault the jury is out at the moment as to whether its fixed or not yet, need to run it a few more times to be sure.

Norfolk Mustard S4s #1 :)

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I've run it up lots of times now since I fitted it and would have expected the stall to manifest at least once by now so I think I can mark that one as solved.

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Norfolk Mustard S4s #1 :)

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