2003 Mustang GT Convertible with a high 2k idle, drops to 1.5 sometimes at a stop. I tried locating any vacuum leak using an unlit propane torch but found that there was no change to idle. I then disconnected the vacuum line at the top of the EGR valve and let it huff some propane gas but still no change. Does the IAC need disconnected for this test? It is an aftermarket throttle body with a brand name and not a horse on it so I adjusted the base idle (using the set screw with the IAC disconnected, tuning it down until it stumbled and almost stalled) but the high idle persists. Are there any common leak locations I can inspect visually since the propane had no impact on the idle?
Note: I pulled off and cleaned the IAC and EGR, and cleaned the MAF with CNC MAF cleaner. previous to checking for leaks. Looks like the previous owner disconnected the O2 sensors with a CAT Delete and it is running real rich. Would that cause the high idle? I'm getting maybe 11 mpg with a feather foot on the throttle...
Note: I pulled off and cleaned the IAC and EGR, and cleaned the MAF with CNC MAF cleaner. previous to checking for leaks. Looks like the previous owner disconnected the O2 sensors with a CAT Delete and it is running real rich. Would that cause the high idle? I'm getting maybe 11 mpg with a feather foot on the throttle...