thank you for all you do, my hero for real! troubleshooting this issue for weeks, in my frustration i slapped the air intake resonator down and the idle went down to normal. i am clueless but the engine races again on restart. smack the resonator a few times idle drops down to 600. ??? gave the customer a rubber mallet for now til i figure this out please help
180,000 miles 4.7 h.o. motor
Check the throttle body and make sure the plate inside it most freely and you might clean it up while your in there. If that's looking good check the throttle position sensor. Hopefully that helps. Edit: forgot one thing also check the throttle cable to make sure it's not damaged or anything
thank you for your reply---everything is tight and nice and clean. i hear a vacuum noise before i hit the resonator with a mallet, then it goes away and the idle drops to normal. i wonder if theres a hairline crack in the plastic casing itself or theres the rubber seal issue to the throttle body, i am so stumped..