SOURCE: 2007 crown vic 4.6 l idles high on startup
This sounds like a normal condition.What happens is the cold start emission reduction component monitor(software program in the computer) is running.
Cold Start Emission Reduction Component Monitor
The Cold Start Emission Reduction Component Monitor was introduced for the 2006 MY on vehicles that meet the
LEV-II emission standards. The monitor works by validating the operation of the components of the system
required to achieve the cold start emission reduction strategy, namely retarded spark timing and elevated idle
airflow.
When the CSER strategy is enabled, the idle air control system will request a higher idle rpm, elevating engine
airflow. While this CSER elevated airflow is requested, the low airflow test compares the measured idle airflow from
the MAF sensor to the commanded idle airflow from the idle air control strategy.
SOURCE: 96 f-150 idles really high
I just solved this problem on my truck after fighting with it for 2 yrs. Mine is the 5.0 though, check your PVC valve and replace if it is bad. After that Take off your IAC and spray down with carb or brake cleaner and scrape all the carbon build up out of it and work the spring inside. you gotta really clean it out though! After that if it's opening and closing easily put it back together and it should work! you might have to adjust the idle a bit to get it all the way. But after doing this my truck went from a 2000 rpm idle down to about a 700! I hope this helps you!!
SOURCE: RPM run high and slow to drop down
a vacuum leak will cause a high idle due to he fact more air is entering the engine which the computer will compensate by adding more fuel. also, a faulty fuel pressure regulator will increase fuel pressure delivering more fuel than required.
look for broken or detatched vacuum hoses. check fuel pressure; 30-50psi
SOURCE: I have a 1987 Susuki Samurai, 1.3 engine. Cold
Yeah it sounds kinda high. There is no adj except for the idle screw on the throttle, the computer does the rest, if it has one. If not, then you can adjust it some how. If carbureted, check for 2 little screws in the front, and check the choke, If throttle body, then just the idle screw, the idle should be around 1000. Hope this helps.
SOURCE: Engine idle problem. Range Rover 4.6 HSE 1998 Have
sorry but you have tried everything i would have done except that i would have checked the engine breather pipes for deterioation like perished or soft and collapsing .you would be surprised how often this is the main cause of this sort of problem
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