Here is an interesting challenge.

My 97 Avant 2.8 automatic runs and starts great. Last spring and before it started immediately with a single turn of the key. During the hot days this summer it needed two quick turns of the key to start. This fall when the temp dropped it again started on the first turn. This temperature effect was confirmed when we had a few days of Indian summer and it again took two turns of the key to start. This was followed by colder weather and it again that takes one key turn. I think the temp change is someplace between 40 and 50 degrees but cant’ be sure. By the way there is no CEL or codes except when it throws a low EGR flow code every few weeks.

So we have below 40-50 degrees quick to start and above 40-50 not as quick to start.

Any ideas beyond moving north in the summer?

 

Not having dug into these engines, I can give you an idea of what I think it is based on my knowledge of typically carbuerated engines.

Sounds like the air/fuel mix.

 

Next summer try turning your key on (engine off) to get your fuel pump to run for about a second. Do this several times. Then try starting the engine.
When it is very hot, there may be not be enough fuel pressure or you may be getting vapor instead of liquid fuel in the fuel injectors.

 

When is the last time you replaced the Coolant temp sensor?

 

When you say it takes two turns of the key, what, in more detail, happens on the first turn? Does the engine turn over? Do you just hear a click? Does nothing at all happen?

 

Sorry --

When it is cold outside - I turn the key, the starter engages, the motor turns over, and it starts immediatly (less than a second) .

When it is warm outside I turn the key, the starter engages, the motor turns over, and it takes a bit longer to start. I am used to flipping the key on quickly and releasing it so it takes twice to start it. If I keep the starter going it takes 3-4 seconds to start instead of less than a second.

This happens when I first start the vehicle in the AM or at the end of the day after it sits in the lot at work. On cold days it is OK but when the outside temp gets above 60 (I'm still trying to figure out what the magic temp is) it takes a bit longer.

 

2 things to check,
1- Just before my fuel pump died it took two times to start when hot, something to do with the internal overloads within the fuel pump being closer together when warm

2- Fuel evap valve

 

Or the CTS sensor is flipping out telling the ECM the engine temp is -55 or something crazy flooding the engine with gas upon start up, or vice versa. If you have a black top CTS sensor, change it with a green or blue one.
This problem won't throw a fault code either.

 

The problem kinda cleared up when the temp dropped below 20 but it came back and was worse when it got to about 30 today.

Just to be sure - I assume the sensor we are talking about is at the bottom of the radiator.

 

I think he was talking about the one on the rear main pipe, passenger side (3 or 4 prongs)