I had this same problem with my Saturn and it was a faulty coolant temp sensor.

 

Is your cranking primer initial pulse (or equivalent) table configured properly? If the wrong values are set (or its partially zero'd out like Ive heard of someone doing) then it wont start until the coolant temp falls back into the range where the values are correct.

 

you're absolutley right. it didnt start again this morning after the drive to work. am i checking the sensor itself and where is the coolant temp sensor that goes to the ecu in the car?

 

Yes. There are two different sensors. One that is for the ecu, and another is for the dash. You want the one that is for the ecu. I'm still unfamiliar with Evo's under the hood, so I am not sure of the location, but likely it is on the thermostat housing or the vicinity. The one for the ECU typically has about 4 wires going into the connecter, where as the one for the dash is typically 1 or 2.

Here is a decent video to show you how to test the sensor itself.


You can do the pot of water method, or what I normally do is put the sensor in a vice (don't crush it!) and just use a grill lighter.

 

So I just unplugged the coolant sensor (at work still) and yes, it barely started but then died right away on a cold start. Plugged it in and it started right up. Wouldn't that tell me that the sensor is working correctly?

 

No. The ECU won't let the car run when it doesn't detect the CTS.

 

The cars tuned on hks vpro and no one in the area has the equipment to tune it.

 

Sounds like you should ditch it and go back to stock ECU.
I have read a lot of "tuned on HKS vpro" lately and the cars/owners appear to come nowhere near the limit of the stock computer.

 

I really hope it's not a tune issue. I'm going to buy a CPS tmmr and see if that's the issue. For the life f me, I cannot get the temp sensor out.

 

Just bought and installed a new coolant temp sensor. Drove it for a bit and left it for 5 minutes. Car started right up so it looks promising. Will update if it does again.

 

Did you test the old one, or did you just replace it in hopes that it would fix it?

Either way I am happy to hear it is back to normal (hopefully!)

 

Well, replacing the cts didn't work as its still dead after it gets up to operating temps. ny other suggestions?

 

Just replaced it.

 

when it's hot, you said it's trying to crank. Does it have fuel? Spark?

 

Edit: theres spark.