Got a 99 olds aurora that wont start cold. earlier id take a lot to shart and after it warms up you could kill it and start it right up.. now it just backfires , almost starts but never will cold

Generally the main reasons a car like this will not start cold is you havea defective coolant sensor or altitude sensor. (maf or baro)

Also if you have some condensation in the fuel this can cause hard cold starts. You can buy HEET at you local parts house and add it to the fuel so the water will mix with the fuel and remove itself.

This car does not have a cold start injector. It uses varios sensors to know the altitide of the car and temperature.

Also if your fuel injectors are partially clogged this can cause hard starts due to the fact that you would not be getting maximum fuel output when needed and also a clogged fuel injector will spit instead of spray.

Fuel will only burn when in the vapor stage so a fine mist spary is what is needed to maintain proper burn. An injection service may be needed if using techron from chevron doesn't clear things up.

Tried to find info on your Olds but failed; wanted to see if your system included a cold start valve or a cold start injector since practically all fuel systems use them. I couldn't determine which your engine uses but it has one of the two and it may be sticky or is not getting voltage because of a corroded connector.

Just a starting point: Have you checked your battery? make sure the CCA (Cold Crank Amps) match the factory recomended, if so how old is the battery, have it tested make sure its still good. Might not be a bad Idea to Check your plugs too. If those two are not the issue, I would start trouble shooting fuel dilevery sys. Ie. Fuel pump, Fliter, Injectors, Injector drivers (coilpack)