Having an issue with excessive high idle on start, does not decrease no matter how long it runs. Also check engine displays when starting but goes off shortly after starting. Any suggestions? Any help is greatly appreciated.
Go out, start it, and tap the gas pedal. Does the rpm die down to a good range? If so, it's normal. Its just your car trying to warm up. You can over ride it by touching the gas pedal.
Vacuum Leak - If it's a 2.8, take the air cleaner tube off. Look in the bottom of the TB. You will see a hole about 10MM. Start the car and then put your finger over the hole. Does it idle down but keeps running? If so - you have a big vac leak - as mentioned above - EGR Tube, Cracked plastic vac line, etc......
Throttle body injection guys come on! The choke remains open to get the vehicle to operating temp haha you release the butterfly valve by tapping the gas pedal.
Just try it. I'm not saying its right but check the simple things first. Then check your vac lines. Get in there with starter ether or brake clean and spray around if you see no visible cracked/ corroded/ split hoses.
Iwould also like to note he said on start, not constantly. But he was vague so we all have a plethora of options to throw at him. We dont ever know if he's on a carb, tbi or fi set up, we dont know if he's ever done the vac lines, we don't know if its the 2.5 or 2.8, manual or auto so theres a lot to consider in this post. He may even have swapped the engine.