XJ12 SII not running... climbing the walls

[Aristides (Aristides Balanos)]

@marsjell

There has been one occurrence where after holding the throtle at 50%, it all of a sudden picked up and rev’'d up, after that it stalled and I was back where I started from.

@marsjell

Replaced the maps sensor,

You mean the vacuum sensor inside the ECU ???

@marsjell

swapped the ECU

Are you sure the replacement ECU is in good working order ?
My gut feeling says ECU… had a similar situation.

[v12-engine] Cold start problem

Dear friends, My 86 V12 HE suddenly developed a cold starting issue and I am a bit at a loss here. Have been troubleshooting for a week with no result. She will fire and idle very roughly. The idle will hunt between 200 and 500 rpm, and after about 15 sec, or as soon as I touch the gas pedal, she dies… After the 19th or so consecutive attempt she will fire and all is fine, will restart with no problem and engine idles and runs flawlessly. Next morning the same story all over again… N…

Hope that helps.