Quote Originally Posted by Quint View Post
It is more likely that you're unstable idle are caused by the following:

1. vacuum leaks
2. fuel delivery issues

For #1, its all intake related.
1. Start from the airbox to MAF, to throttle body.
2. Then look for all small rubber hose connections to and from the intake. Replace.
3. Check for air leaks on oil filler cap, dipstick, etc.

The best way to do this is to do a smoke test. Run a line a la smoke machine at around 2-3 psi into intake, and see where the leaks are coming from. Some people use carb cleaner and spray the portions of intake while in idle. When you have a leak, you will notice that your idle will suddenly surge. Then, you can identify the leak. Problem with this method is that it does not identify small leaks, which is likely what you have. Small leaks manifest only when the engine is cold, because when its hot, rubber expands, and sometimes it closes the leak. Maybe that's why it takes your car 5 min before it stabilizes.

For #2:
1. Check/ replace fuel filter.
2. Check fuel lines.
3. Check fuel pressure at the fuel pump and the fuel rail.

There could be other causes i.e. sticky throttle position sensors, or even an old oxygen sensor that might be needing replacement. Also check for sticky idle control valve, if you have. Best to diagnose via OBD scanner, if possible.


Thanks Bro!