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When starting cold engine, the engine idles around 1700 rpm for a little while before coming down to normal. Is this 1700 rpm normal after start or a little high?
Higher than normal idle has also occured for these reasons: dirty MAF, vacuum leak, sticky throttle plate, dirty or malfunctioning IAC, binding throttle linkage.
My 98 has a new IAC and it starts at 1500 rpm and goes down to 900 rpm within 15-20 seconds. I thought it was normal. I will have to start checking out the items tsdrallyer outlined.
Just got back from the Christmas holidays, thanks for the replies. I"ll check those items listed, but i'm definitely going to change the iac valve. My expy has 79,000 now. The couple i bought it from did tell me they had changed it once around 40,000 when it failed to start. I think its due and i wouldn't be in the least bit surprised this fixes the high idle speed on startup.
Don't fret your high idle, provided it is just for a few seconds. I read a "poll" type thread regarding this a couple years ago and most everybody's 5.4 or 4.6 idled very high (between 1,200 and 1,800) for a few seconds then progressively returned back to a normal idle (500 to 700). A few of the guys even explained why this is absolutely normal for these motors. I doubt a faulty IAC valve is the problem, inasmuch as its symptoms are opposite a high idle.
It is normal for your engine to idle a little higher when you first start it. Mine idles at 1600 when I first start it, then it drops to 1400 after 2 seconds, and then to 1100 after 6 seconds, and then drops down to 900 after a little while, which is when I turned the truck off and went back inside. Mine does idle lower after the truck is completely warmed up.
Thanks again for the replies. Went this morning and started it up to be a little more accurate. Outside temp was about 40. It first idled at 1700 for 5 seconds, 1600 for 5 seconds, then over the next five seconds came on down to 1200, then a 1000. It stayed at 1000 as i'm sure it needed time to get warmed up a little before coming back down to normal. If this is normal than so be it, the truck runs and drives fine.
My 92 dakota with a 318 never breaks a 1000 on startup. I'm a little puzzled at the variation from the different posts. Some mentioned 1000 or 1200 rpms. I understand that the colder it is outside the longer these idle speeds will stay up, but even in the summertime it went to 1700 and would take at least 10-15 seconds before working its way to normal idle speed.