I have an 02 Mercury Mountaineer. It won’t start unless I hold the gas down and as soon as I let off the gas it dies. Any guesses? Thanks.
Well a very good gues would be a sludged up or defective IAC/idle air control valve.
Some folks have good luck with simply cleaning the IAC. Or for about 60 bucks you can buy a new one at Napa or Autozone. Replacing it takes about 5 minutes.
Heres a link with everything you ever wanted to know about the IAC