high start up idle???
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Fleet Mechanic
Joined: Dec 2004
Posts: 1,365
Likes: 6
From: Ketchikan, AK.
high start up idle???
hi, i have a 99 f250 SD with the 5.4. when i start it in the morning, it seems to run a little high to me... around 1500 rpm's at first, and then after about 30-40 seconds it will slowly kick down to about 1200 or so. all and all, it takes about 5 minutes to get down to 700-800 rpm. we have had temps lately around 38-40. when it finally warms up, it seems to have a slightly uneven idle. could this be the idle air control valve going bad?? would that throw a code to turn on the engine light? the light hasd not come on at all. what else could do this..... i recently changed the plugs and the #4 cop due to the known missing problem . but the idle seems off to me. what else could i check before i go and dump 60.00 away on this valve?? thanks !
Senior User
Joined: Feb 2003
Posts: 206
Likes: 0
From: Long Island, NY
My '98 Expedition 5.4L does the same thing, but the high idle only lasts about 10 seconds and it goes down to around 1,000 rpm for about another 10 seconds then it goes to around 700. Have you tried cleaning your MAS (mass air flow sensor), throttle body valve? etc...
