Having an issue with my 07 matrix. Starts fine when engine is cold and it runs great. But if I stop after the engine is warm, it dont want to start till it sits for awhile. It turns over just won't fire. Any ideas what might cause this?
there are many things that can cause a no start warm problem. Scanning the engine when it is cold and comparing it to when it is warm and won't start would be the easiest way to see what is going on. If your coolant sensor reads too cold your engine would work fine when cold because it will run rich. After it warms up that rich condition could become a flooding problem that would make it difficult to start. When it won't start, try holding the gas pedal to the flood and see if you can get it to start up that way. (release the pedal as soon as it starts up. don't hold it down and let the engine race away when it starts)
Could be a fuel pump problem. When the fuel pump gets hot it turns off until it cools down.
It could be a fuel pressure regulator which acts just like a temp sensor, makes it rich when warm.
could be a bad coil or module that gets hot and stops working.
Checking for spark, fuel pressure and injector pulse when it won't start would be the first things to do. See if you are missing any one or more of those things would where to pinpoint your diagnosis.