ok i'm pretty good with cars and diagnosing them but this ones got me stumped big time, ok so i bought the car about 3 weeks ago and i brought it home and noticed that sometimes when i try to start the car the D4 light blinks and the car woulnt start, so after research and using a jumper wire to pull the codes i found out i have a bad tcu, ok but like i said it only does it sometimes, but as long as the D4 light wasnt blinking the car would start, but about a week ago i figured out that when the tempeture outside is hot and the car is getting direct sunlight i have hardstarting problems which lead to the D4 light to start blinking, so last night i got home from work and had to rush to the hospital for my daughter and the car ran fine on the parkway hitting about 95 MPH and after i was done with the hospital it was cool out and the car started right up with no problem at all, but about an hour ago i tried going out to my car and starting to drive to the store and of course its hot out today and usually my car will start for a second and stall and ill wait about 2 minutes and it will start right up but this time the car just cranks and woulnt start at all. like i said it ONLY does this when it is hot outside, but when its cool or cloudy or rainy the car starts with no problem. and like i said before when the D4 light blinks the car woulnt start but this time the D4 light wasnt blinking and the Check Engine Light wasnt on either, so what could my problem be here?

 

Main relays inside the car do not like hot temps. Car closed up, is gets really hot inside, open the door and leave it open they cool off. Not 100% sure that is the issue but it is my bet right now. When it will not start, what is missing (spark, fuel, air)? Need to break it down to know where to start.

 

Yeh, I concur on the main relay..........apparently quite a common failure as you no doubt will find looking through the threads on here.

I had the same issue, I located the said main relay (in the footwell attached to the steering column), took it out, re-soldered all the joints and lubed up the actual mechanism and hey presto haven't had a single splutter since.

hope this helps

Tony