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S4S runs perfect until hot then rough / stalls / rough idle on restart

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Had been sitting for about 2 months .....

Battery got quite flat but not completely dead.

Runs perfectly for about 10 minutes and then runs rough , stalls and if restarted while hot idles rough and stalls. No CEL / No battery light

Leave it to cool and it great again for 10 minutes......

Is not overheating - 80-85C 

I am wondering about coils / leads / IAC valve....Something is playing up when hot...can a fuel pump issue do this despite being able to maintain high revs first 10 minutes? 

How can I check what the IAC should be doing with freescan ?

Anything else to check? I did put 100 octane in it about 6 months ago....I know that stuff can go bad pretty quick...but doesn't seem consistent with that 

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  • Gold FFM

Sounds very similar to what mine did when the O2 sensor died. Freescan/Espritmon should tell you whether its working correctly or not.

Norfolk Mustard S4s #1 :)

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  • Moderator

Have you checked the O2 readings? Always better to verify before fitting new parts. 😉

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.


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