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1990 mx5 g4x pnp Doesn't start when cold


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I'm a hefty chunk lost in my tuning adventure as I installed the pnp link g4x into my 1990 1.6L mx5 with 380cc injectors.

I got it up and running with a jump start initially and I've been running it ok with my blocked out fuel table. But when it comes to starting of a morning (around 10°C), it just doesn't start, it won't even try and fire. It's only a little bit better when it's a warmer ambient temperature with me being able to start after a couple cranks when the engine is cold.

I noticed while logging, that my afr dips down to 10.2 a couple frames after the rpm picks up before going back to stoich, but that's while the engine is somewhat warm, not sure if that's relevant but yeah.

I know my tune is probably bad, but I'm tryin' my hardest to learn


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Crank enrichment is typically quite a bit higher than you have so I would start experimenting with that.  Your numbers in black compared to one of my cars in yellow below.  Id probably double the numbers you have in the pre-crank prime also.  

In idle settings give it more start up offset so it gets more airflow during cranking, make the startup hold and decay much shorter (say about 1sec each) so you dont get a big flare after starting.  

In the main fuel table I would probably copy the 500RPM column to the 0RPM column so you have less variables affecting fuel volume during cranking (or just delete the 0rpm column). 

IAT fuel trim table should be turned off with modeled mode too. 

Not related to starting, but your accel fuel needs non-zero values in the cold correction table - this is a multiplier so 0 means no accel enrichment at all.  It should be 1.0 at normal operating temp and usually higher at low temps.

If none of that helps then we will need to see a log.  



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I gave your recommendations a go and it seems to be a lot happier to start, but it still takes a couple cranks before it decides to pick up. Definitely onto something there, I thank you for your help, I'll keep adjusting to find out what works and I'll probably post an update tomorrow morning if I don't get the car started in the cold.

Thanks again

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