Boxster Starting Issue
 

Anyone have an idea why my Boxster has trouble starting and stay running when it is warmed up or is a hot day? It sputters and dies off if I don't keep it revved up for a bit, then it will run fine. This only happens on start when it is a warmed up engine or on a hot day.

Note: The Air Mass Sensor has been replaced and still happens.

What codes does it show.

Can you elaborate on the sputtering? Is the car turning over, then the idle is out of whack and it stalls, or do you mean that the starter is sputtering and it never turns over?

What year is it? Any codes, other issues?

A failing CPS will often not throw a code and will be finicky when hot, other suggestions based on limited info: fuel pump, or a very dirty throttle and/or control valve. Again, these are guesses based on limited information.

The car is 1999 Boxster. It turns over fine. Rather than instant start it takes a few seconds and helps if I pump the gas. It runs fine once started. Not sure on codes. The check engine light has come on now. We just replaced the Sensor.

You are imagining things. Pumping the pedal has zero effect on starting. That only worked on carbureted engines with acceleration pumps. :-)

My bet is that you've got a vacuum leak. First thing I'd check is the oil filler tube.

Do a resistance test(hot) on the CPS

Not true on a '99. Pressing the pedal opens the butterfly on the throttle body (he has a cable throttle).

Sounds like an EVAP regeneration valve based on the symptoms. Could also be CPS, MAF or fuel sending unit.
Is it hard to start after fueling, or only when hot?
You say "we just replaced the sensor"...which sensor?

Here's a good post on the regeneration valve:
http://986forum.com/forums/performance-technical-chat/50264-success-finally-fixed-hard-start-while-hot-fueling-issues.html