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

[pureguava]

Hi

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 

[Chillidoggy]

Maybe do a Freescan log first? From cold, up to when the problem occurs. It might point you in the right direction. 

[tomcattom]

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

[pureguava]

Thanks - I put the non lotus O2 sensor in about 4 years ago.  Have ordered a Delphi lotus one.   Will update ….

[Escape]

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

[cammmy]

Is 100 octane leaded?

Another thought could be the carbon cannister. Try blanking the port (at the front of the manifold, near the firewall) just to see if that helps.

[pureguava]

Solved ! 
 

it was the O2 sensor.   Fitted a lotus spec one and it’s all resolved.   Thanks for all the help 

 

Al