# Switching from CHTS to FTS signal during startup.



## CoorsZ31 (May 16, 2010)

"84-85 ECU’s (all) have been reported to have a small lean surge problem during the first 30 seconds or so of engine warm up. This is most likely an issue with the cold-start enrichment and can be remedied by switching from CHTS to FTS signal during startup."

Found this little tidbit on red's page. I do find that after I get past cold start if I unplug the chts my car loses the lean startup issue. Is this suggesting to install some sort of toggle to disable the chts? Kind of a pain having to physically unplug the chts a minute after every cold start.

Probably going to just change my ecu to an 87 model. But, am I correct in my assumption on how to change startup signal?


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## CoorsZ31 (May 16, 2010)

*Warm Up Problem, Lean surge Problem*

Well regardless, changing my 85 ecu out for an 87 ecu was a great success. After battling the lean surge warm up for a couple years, turns out this fixed it.

I chose an 87 ecu because no wiring or sensor changes were necessary, just plug and play baby.

Car has never ran better! :jump:

*Z31 300ZX Fuel System Configurations*

*Read this page before doing any ecu changes, it will let you know if any sensor changes or resistors need to be wired into your electronics.*

84 85 300xz z31


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