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EVO 9 Cold Start

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Hello, I am dealing with an idle issue on an EVO 9 running Tephra mod. On cold start, the car starts, then immediately cuts out unless throttle is applied. Car idles sometimes when warmed up. It is running speed density, it is a high compression motor with 272 cams, fic 1650s, resistor mod, and an FP Black. I added 2* of timing at idle and pulled out some fuel from the VE map, but its still not perfect. Any suggestions on what else to look at? This is my first evo im working with so any input is well appreciated.


You need to increase fuel injection primer pulse, cranking injection pulse width and post start enrichment decay. You can get details from Merlins guide 1.7 or from forum...

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the thing is i don’t see a decay table with the definitions i tried for tephramod. but i appreciate the tips

What ROM are you using?

it’s 88591715. The car only likes to idle smoothly really rich at like 7:1 to 9:1, anything above it doesn’t stay running and shuts off

Can you send me your ROM file and idle log?

I’m really sorry I wasted your time it turns out his wideband gauge was reading 30 to 40% too rich. when we swapped out for the aem xseries it ran perfectly fine hitting stoich.

Great. But anyway i went on Enternet and found that ROM and definition file- indeed it is very poor. I would advise to switch for another Tephra mod ROM that has more options for good engine tuning.

which would you suggest? i’m open to any recommendations i’m just taking over where someone left off. i’m way more familiar with subarus so any evo advice is well appreciated

Let me do some homework to find out what ROMs are compatible with USDM Evo 9. I'll get back to you soon.

Unfortunately it looks like there is only one tephra option for USDM Evo 9s... Anyway, if you'll have any questions feel free to ask...