my truck does the same thing as well as my old one. I used to own a 1991 f-150 that would just SCREEEEEEEEEEAAMM when I started it. now my new truck has the 5.4L in it an not only does it rev high when first started but runs like total animal **** after it chills out, this truck is really pissin me off really really bad my old man and i replaced the computer, injectors, and a COMPLETE tune up, and now last night, the idle air control all factory parts. Ran good on the way to school this mornin but like total crap on the way back, GOD I I""M PISST I just don't know what else to do and I'm broke untill next paycheck. I was gonna get some duals put on it but screw that. That might things worse.

BTW- my exhaust is in top shape, I had the catalytic converter checked, checks out great with only 2 lbs of restriction. WHAT TO DO, WHAT TO DO, WHAT TO DO!!!!!!!!!!!

 

I recently "cleaned out" my IAC valve with TB cleaner spray, for a day or two afterwards it would idle like you guys are describing when cold. After that, it stopped and went back to normal. I also replaced one of the 02 sensors at the same time. Now I'm not sure if it was the cleaning or the new 02 sensor that did it. It sounds like a wierd sensor problem to me, but I'm no expert I feel for you guys.,,,,98

 

Wow I am amazed that the Sr. Members have stayed away from this topic!

f150-91 its sounds like you missed the entire egr sustem!(Not just the valve) good luck

now fx402 a couple of questions for you...when you start the truck do you have anything on like the heat or defrost? Or an aftermarket stereo?

it sounds like i wouldn't worry to much about what is going on, these trucks (As is all new vehicles) are controlled by the computer and when you first start the truck there are a lot of factors taking place at the same time (Out side temp,humidity,ac compressor on/off, heavy load on alternator, fuel mixture, oxegen content, etc,etc)and it takes a little while for the computer to sort all of this stuff out and then make its adjustment. In addtion the idle is supposed to go up when you put in in gear so that you don't stall, the idle should go up when the ac compressor is on (in all defrost settings and a/c settings and sometimes the panel setting)

If it starts to jump over 1000 rpm then you have issues!

good luck!!

 

I heard that it does that on purpose to burn off the excess gas that sits in the combustion chambers and fuel rail at startup. Since the engine is cold, it's very inefficient, so it idles high like to prevent excess pollutants from entering the atmosphere and to burn up all the gas.

I wouldn't worry about it. It won't hurt anything. Mine does it to.

 

ok I guess i feel better about the high idle problem but it never did this for a month after i bought it with on;y 12K on it. I've had the truck for 2 mon. now and overall it runs good but not to it's potential and the rough idle could be just a messed up egr valve or somethin, I'll plug it off and run the truck and see what happens, I'll let you know my truck now has 15K on it (I like to drive my truck and so des my old man )

 

Don't plug the EGR!! Once the engine is hot it will detonate very badly! Most likely the EGR valve is fine but the rest of the "EGR" system is clogged.

Also depending on how many miles you have on the truck your throttle body could be dirty. With these computer engines even the slightest amount of dirt can alter the idle bypass airflow so the computer will constantly re-adjust the idle. Pull of the air intake tube and rub your finger around the throttle plate, if your finger comes out dirty you need to clean it! DO NOT USE CARB CLEANER!!

Good luck!!

 

Wow, I never thought anyone would have replied since I posted the last comment in March.

Ernie,
It seems that I have the same problem that you described. Ever since that last visit (3rd time) to the dealer, it never really happened to me again. However, I used to be like a lot of people and let it "warm up" a little like you do but I got so angry with it that now, I start it up, let sit for about a min or two and off I go. You can say that I don't let it idle long enough to have the problem come up. Other than that, I don't have any engine problems with the truck. Also, since then, I changed my air filter to a drop in K&N and used Mobil 1 5W30 in the engine. I don't think this affects it but I just wanted to state it.

hcmq,
No, I don't have anything "on" when I start the truck up. I usually turn everything off before I shut the engine. Its a habit, I guess.

Does anyone have a problem with the passenger side window rubbing on the outside gasket, causing a obnoxious noise everytime the window goes up and down? I'm gonna post this in the body section but I figure I can insert it here as well.

Thanks for the replies...

 

Fx402:

I resurrected your thread as a result of a search for folks with similar idling annomalies. Your's seemed to be the most similar to mine. Glad to hear you've learned to live with it.......I hope it's just "one of those things", and doesn't become a bigger problem. Let's hope for the best........however, I will still mention it to my service guy just to get it "on the record" in case of future problems. Other than that, I love my truck. Continued good luck with yours.

ernie